Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Read-Copy Update mechanism for mutual exclusion (tree-based version) |
| 3 | * Internal non-public definitions that provide either classic |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 4 | * or preemptible semantics. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 5 | * |
| 6 | * This program is free software; you can redistribute it and/or modify |
| 7 | * it under the terms of the GNU General Public License as published by |
| 8 | * the Free Software Foundation; either version 2 of the License, or |
| 9 | * (at your option) any later version. |
| 10 | * |
| 11 | * This program is distributed in the hope that it will be useful, |
| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | * GNU General Public License for more details. |
| 15 | * |
| 16 | * You should have received a copy of the GNU General Public License |
| 17 | * along with this program; if not, write to the Free Software |
| 18 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 19 | * |
| 20 | * Copyright Red Hat, 2009 |
| 21 | * Copyright IBM Corporation, 2009 |
| 22 | * |
| 23 | * Author: Ingo Molnar <mingo@elte.hu> |
| 24 | * Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
| 25 | */ |
| 26 | |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 27 | #include <linux/delay.h> |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 28 | |
Mike Galbraith | 5b61b0b | 2011-08-19 11:39:11 -0700 | [diff] [blame] | 29 | #define RCU_KTHREAD_PRIO 1 |
| 30 | |
| 31 | #ifdef CONFIG_RCU_BOOST |
| 32 | #define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO |
| 33 | #else |
| 34 | #define RCU_BOOST_PRIO RCU_KTHREAD_PRIO |
| 35 | #endif |
| 36 | |
Paul E. McKenney | 26845c2 | 2010-04-13 14:19:23 -0700 | [diff] [blame] | 37 | /* |
| 38 | * Check the RCU kernel configuration parameters and print informative |
| 39 | * messages about anything out of the ordinary. If you like #ifdef, you |
| 40 | * will love this function. |
| 41 | */ |
| 42 | static void __init rcu_bootup_announce_oddness(void) |
| 43 | { |
| 44 | #ifdef CONFIG_RCU_TRACE |
| 45 | printk(KERN_INFO "\tRCU debugfs-based tracing is enabled.\n"); |
| 46 | #endif |
| 47 | #if (defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 64) || (!defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 32) |
| 48 | printk(KERN_INFO "\tCONFIG_RCU_FANOUT set to non-default value of %d\n", |
| 49 | CONFIG_RCU_FANOUT); |
| 50 | #endif |
| 51 | #ifdef CONFIG_RCU_FANOUT_EXACT |
| 52 | printk(KERN_INFO "\tHierarchical RCU autobalancing is disabled.\n"); |
| 53 | #endif |
| 54 | #ifdef CONFIG_RCU_FAST_NO_HZ |
| 55 | printk(KERN_INFO |
| 56 | "\tRCU dyntick-idle grace-period acceleration is enabled.\n"); |
| 57 | #endif |
| 58 | #ifdef CONFIG_PROVE_RCU |
| 59 | printk(KERN_INFO "\tRCU lockdep checking is enabled.\n"); |
| 60 | #endif |
| 61 | #ifdef CONFIG_RCU_TORTURE_TEST_RUNNABLE |
| 62 | printk(KERN_INFO "\tRCU torture testing starts during boot.\n"); |
| 63 | #endif |
Paul E. McKenney | 81a294c | 2010-08-30 09:52:50 -0700 | [diff] [blame] | 64 | #if defined(CONFIG_TREE_PREEMPT_RCU) && !defined(CONFIG_RCU_CPU_STALL_VERBOSE) |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 65 | printk(KERN_INFO "\tDump stacks of tasks blocking RCU-preempt GP.\n"); |
| 66 | #endif |
| 67 | #if defined(CONFIG_RCU_CPU_STALL_INFO) |
| 68 | printk(KERN_INFO "\tAdditional per-CPU info printed with stalls.\n"); |
Paul E. McKenney | 26845c2 | 2010-04-13 14:19:23 -0700 | [diff] [blame] | 69 | #endif |
| 70 | #if NUM_RCU_LVL_4 != 0 |
Paul E. McKenney | cc5df65 | 2012-06-15 18:16:00 -0700 | [diff] [blame] | 71 | printk(KERN_INFO "\tFour-level hierarchy is enabled.\n"); |
Paul E. McKenney | 26845c2 | 2010-04-13 14:19:23 -0700 | [diff] [blame] | 72 | #endif |
Paul E. McKenney | f885b7f | 2012-04-23 15:52:53 -0700 | [diff] [blame] | 73 | if (rcu_fanout_leaf != CONFIG_RCU_FANOUT_LEAF) |
| 74 | printk(KERN_INFO "\tExperimental boot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf); |
Paul E. McKenney | cca6f39 | 2012-05-08 21:00:28 -0700 | [diff] [blame] | 75 | if (nr_cpu_ids != NR_CPUS) |
| 76 | printk(KERN_INFO "\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids); |
Paul E. McKenney | 26845c2 | 2010-04-13 14:19:23 -0700 | [diff] [blame] | 77 | } |
| 78 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 79 | #ifdef CONFIG_TREE_PREEMPT_RCU |
| 80 | |
Paul E. McKenney | 037b64e | 2012-05-28 23:26:01 -0700 | [diff] [blame] | 81 | struct rcu_state rcu_preempt_state = |
| 82 | RCU_STATE_INITIALIZER(rcu_preempt, call_rcu); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 83 | DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 84 | static struct rcu_state *rcu_state = &rcu_preempt_state; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 85 | |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 86 | static int rcu_preempted_readers_exp(struct rcu_node *rnp); |
| 87 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 88 | /* |
| 89 | * Tell them what RCU they are running. |
| 90 | */ |
Paul E. McKenney | 0e0fc1c | 2009-11-11 11:28:06 -0800 | [diff] [blame] | 91 | static void __init rcu_bootup_announce(void) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 92 | { |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 93 | printk(KERN_INFO "Preemptible hierarchical RCU implementation.\n"); |
Paul E. McKenney | 26845c2 | 2010-04-13 14:19:23 -0700 | [diff] [blame] | 94 | rcu_bootup_announce_oddness(); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 95 | } |
| 96 | |
| 97 | /* |
| 98 | * Return the number of RCU-preempt batches processed thus far |
| 99 | * for debug and statistics. |
| 100 | */ |
| 101 | long rcu_batches_completed_preempt(void) |
| 102 | { |
| 103 | return rcu_preempt_state.completed; |
| 104 | } |
| 105 | EXPORT_SYMBOL_GPL(rcu_batches_completed_preempt); |
| 106 | |
| 107 | /* |
| 108 | * Return the number of RCU batches processed thus far for debug & stats. |
| 109 | */ |
| 110 | long rcu_batches_completed(void) |
| 111 | { |
| 112 | return rcu_batches_completed_preempt(); |
| 113 | } |
| 114 | EXPORT_SYMBOL_GPL(rcu_batches_completed); |
| 115 | |
| 116 | /* |
Paul E. McKenney | bf66f18 | 2010-01-04 15:09:10 -0800 | [diff] [blame] | 117 | * Force a quiescent state for preemptible RCU. |
| 118 | */ |
| 119 | void rcu_force_quiescent_state(void) |
| 120 | { |
| 121 | force_quiescent_state(&rcu_preempt_state, 0); |
| 122 | } |
| 123 | EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); |
| 124 | |
| 125 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 126 | * Record a preemptible-RCU quiescent state for the specified CPU. Note |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 127 | * that this just means that the task currently running on the CPU is |
| 128 | * not in a quiescent state. There might be any number of tasks blocked |
| 129 | * while in an RCU read-side critical section. |
Paul E. McKenney | 25502a6 | 2010-04-01 17:37:01 -0700 | [diff] [blame] | 130 | * |
| 131 | * Unlike the other rcu_*_qs() functions, callers to this function |
| 132 | * must disable irqs in order to protect the assignment to |
| 133 | * ->rcu_read_unlock_special. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 134 | */ |
Paul E. McKenney | c3422be | 2009-09-13 09:15:10 -0700 | [diff] [blame] | 135 | static void rcu_preempt_qs(int cpu) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 136 | { |
| 137 | struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu); |
Paul E. McKenney | 25502a6 | 2010-04-01 17:37:01 -0700 | [diff] [blame] | 138 | |
Paul E. McKenney | e4cc1f2 | 2011-06-27 00:17:43 -0700 | [diff] [blame] | 139 | rdp->passed_quiesce_gpnum = rdp->gpnum; |
Paul E. McKenney | c3422be | 2009-09-13 09:15:10 -0700 | [diff] [blame] | 140 | barrier(); |
Paul E. McKenney | e4cc1f2 | 2011-06-27 00:17:43 -0700 | [diff] [blame] | 141 | if (rdp->passed_quiesce == 0) |
Paul E. McKenney | d4c08f2 | 2011-06-25 06:36:56 -0700 | [diff] [blame] | 142 | trace_rcu_grace_period("rcu_preempt", rdp->gpnum, "cpuqs"); |
Paul E. McKenney | e4cc1f2 | 2011-06-27 00:17:43 -0700 | [diff] [blame] | 143 | rdp->passed_quiesce = 1; |
Paul E. McKenney | 25502a6 | 2010-04-01 17:37:01 -0700 | [diff] [blame] | 144 | current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 145 | } |
| 146 | |
| 147 | /* |
Paul E. McKenney | c3422be | 2009-09-13 09:15:10 -0700 | [diff] [blame] | 148 | * We have entered the scheduler, and the current task might soon be |
| 149 | * context-switched away from. If this task is in an RCU read-side |
| 150 | * critical section, we will no longer be able to rely on the CPU to |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 151 | * record that fact, so we enqueue the task on the blkd_tasks list. |
| 152 | * The task will dequeue itself when it exits the outermost enclosing |
| 153 | * RCU read-side critical section. Therefore, the current grace period |
| 154 | * cannot be permitted to complete until the blkd_tasks list entries |
| 155 | * predating the current grace period drain, in other words, until |
| 156 | * rnp->gp_tasks becomes NULL. |
Paul E. McKenney | c3422be | 2009-09-13 09:15:10 -0700 | [diff] [blame] | 157 | * |
| 158 | * Caller must disable preemption. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 159 | */ |
Paul E. McKenney | cba6d0d | 2012-07-02 07:08:42 -0700 | [diff] [blame] | 160 | static void rcu_preempt_note_context_switch(int cpu) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 161 | { |
| 162 | struct task_struct *t = current; |
Paul E. McKenney | c3422be | 2009-09-13 09:15:10 -0700 | [diff] [blame] | 163 | unsigned long flags; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 164 | struct rcu_data *rdp; |
| 165 | struct rcu_node *rnp; |
| 166 | |
Paul E. McKenney | 10f39bb | 2011-07-17 21:14:35 -0700 | [diff] [blame] | 167 | if (t->rcu_read_lock_nesting > 0 && |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 168 | (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) { |
| 169 | |
| 170 | /* Possibly blocking in an RCU read-side critical section. */ |
Paul E. McKenney | cba6d0d | 2012-07-02 07:08:42 -0700 | [diff] [blame] | 171 | rdp = per_cpu_ptr(rcu_preempt_state.rda, cpu); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 172 | rnp = rdp->mynode; |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 173 | raw_spin_lock_irqsave(&rnp->lock, flags); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 174 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; |
Paul E. McKenney | 8684896 | 2009-08-27 15:00:12 -0700 | [diff] [blame] | 175 | t->rcu_blocked_node = rnp; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 176 | |
| 177 | /* |
| 178 | * If this CPU has already checked in, then this task |
| 179 | * will hold up the next grace period rather than the |
| 180 | * current grace period. Queue the task accordingly. |
| 181 | * If the task is queued for the current grace period |
| 182 | * (i.e., this CPU has not yet passed through a quiescent |
| 183 | * state for the current grace period), then as long |
| 184 | * as that task remains queued, the current grace period |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 185 | * cannot end. Note that there is some uncertainty as |
| 186 | * to exactly when the current grace period started. |
| 187 | * We take a conservative approach, which can result |
| 188 | * in unnecessarily waiting on tasks that started very |
| 189 | * slightly after the current grace period began. C'est |
| 190 | * la vie!!! |
Paul E. McKenney | b0e165c | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 191 | * |
| 192 | * But first, note that the current CPU must still be |
| 193 | * on line! |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 194 | */ |
Paul E. McKenney | b0e165c | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 195 | WARN_ON_ONCE((rdp->grpmask & rnp->qsmaskinit) == 0); |
Paul E. McKenney | e7d8842 | 2009-09-18 09:50:18 -0700 | [diff] [blame] | 196 | WARN_ON_ONCE(!list_empty(&t->rcu_node_entry)); |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 197 | if ((rnp->qsmask & rdp->grpmask) && rnp->gp_tasks != NULL) { |
| 198 | list_add(&t->rcu_node_entry, rnp->gp_tasks->prev); |
| 199 | rnp->gp_tasks = &t->rcu_node_entry; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 200 | #ifdef CONFIG_RCU_BOOST |
| 201 | if (rnp->boost_tasks != NULL) |
| 202 | rnp->boost_tasks = rnp->gp_tasks; |
| 203 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 204 | } else { |
| 205 | list_add(&t->rcu_node_entry, &rnp->blkd_tasks); |
| 206 | if (rnp->qsmask & rdp->grpmask) |
| 207 | rnp->gp_tasks = &t->rcu_node_entry; |
| 208 | } |
Paul E. McKenney | d4c08f2 | 2011-06-25 06:36:56 -0700 | [diff] [blame] | 209 | trace_rcu_preempt_task(rdp->rsp->name, |
| 210 | t->pid, |
| 211 | (rnp->qsmask & rdp->grpmask) |
| 212 | ? rnp->gpnum |
| 213 | : rnp->gpnum + 1); |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 214 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | 10f39bb | 2011-07-17 21:14:35 -0700 | [diff] [blame] | 215 | } else if (t->rcu_read_lock_nesting < 0 && |
| 216 | t->rcu_read_unlock_special) { |
| 217 | |
| 218 | /* |
| 219 | * Complete exit from RCU read-side critical section on |
| 220 | * behalf of preempted instance of __rcu_read_unlock(). |
| 221 | */ |
| 222 | rcu_read_unlock_special(t); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 223 | } |
| 224 | |
| 225 | /* |
| 226 | * Either we were not in an RCU read-side critical section to |
| 227 | * begin with, or we have now recorded that critical section |
| 228 | * globally. Either way, we can now note a quiescent state |
| 229 | * for this CPU. Again, if we were in an RCU read-side critical |
| 230 | * section, and if that critical section was blocking the current |
| 231 | * grace period, then the fact that the task has been enqueued |
| 232 | * means that we continue to block the current grace period. |
| 233 | */ |
Paul E. McKenney | e7d8842 | 2009-09-18 09:50:18 -0700 | [diff] [blame] | 234 | local_irq_save(flags); |
Paul E. McKenney | cba6d0d | 2012-07-02 07:08:42 -0700 | [diff] [blame] | 235 | rcu_preempt_qs(cpu); |
Paul E. McKenney | e7d8842 | 2009-09-18 09:50:18 -0700 | [diff] [blame] | 236 | local_irq_restore(flags); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 237 | } |
| 238 | |
| 239 | /* |
Paul E. McKenney | fc2219d | 2009-09-23 09:50:41 -0700 | [diff] [blame] | 240 | * Check for preempted RCU readers blocking the current grace period |
| 241 | * for the specified rcu_node structure. If the caller needs a reliable |
| 242 | * answer, it must hold the rcu_node's ->lock. |
| 243 | */ |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 244 | static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) |
Paul E. McKenney | fc2219d | 2009-09-23 09:50:41 -0700 | [diff] [blame] | 245 | { |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 246 | return rnp->gp_tasks != NULL; |
Paul E. McKenney | fc2219d | 2009-09-23 09:50:41 -0700 | [diff] [blame] | 247 | } |
| 248 | |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 249 | /* |
| 250 | * Record a quiescent state for all tasks that were previously queued |
| 251 | * on the specified rcu_node structure and that were blocking the current |
| 252 | * RCU grace period. The caller must hold the specified rnp->lock with |
| 253 | * irqs disabled, and this lock is released upon return, but irqs remain |
| 254 | * disabled. |
| 255 | */ |
Paul E. McKenney | d3f6bad | 2009-12-02 12:10:13 -0800 | [diff] [blame] | 256 | static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags) |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 257 | __releases(rnp->lock) |
| 258 | { |
| 259 | unsigned long mask; |
| 260 | struct rcu_node *rnp_p; |
| 261 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 262 | if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 263 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 264 | return; /* Still need more quiescent states! */ |
| 265 | } |
| 266 | |
| 267 | rnp_p = rnp->parent; |
| 268 | if (rnp_p == NULL) { |
| 269 | /* |
| 270 | * Either there is only one rcu_node in the tree, |
| 271 | * or tasks were kicked up to root rcu_node due to |
| 272 | * CPUs going offline. |
| 273 | */ |
Paul E. McKenney | d3f6bad | 2009-12-02 12:10:13 -0800 | [diff] [blame] | 274 | rcu_report_qs_rsp(&rcu_preempt_state, flags); |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 275 | return; |
| 276 | } |
| 277 | |
| 278 | /* Report up the rest of the hierarchy. */ |
| 279 | mask = rnp->grpmask; |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 280 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| 281 | raw_spin_lock(&rnp_p->lock); /* irqs already disabled. */ |
Paul E. McKenney | d3f6bad | 2009-12-02 12:10:13 -0800 | [diff] [blame] | 282 | rcu_report_qs_rnp(mask, &rcu_preempt_state, rnp_p, flags); |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 283 | } |
| 284 | |
| 285 | /* |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 286 | * Advance a ->blkd_tasks-list pointer to the next entry, instead |
| 287 | * returning NULL if at the end of the list. |
| 288 | */ |
| 289 | static struct list_head *rcu_next_node_entry(struct task_struct *t, |
| 290 | struct rcu_node *rnp) |
| 291 | { |
| 292 | struct list_head *np; |
| 293 | |
| 294 | np = t->rcu_node_entry.next; |
| 295 | if (np == &rnp->blkd_tasks) |
| 296 | np = NULL; |
| 297 | return np; |
| 298 | } |
| 299 | |
| 300 | /* |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 301 | * Handle special cases during rcu_read_unlock(), such as needing to |
| 302 | * notify RCU core processing or task having blocked during the RCU |
| 303 | * read-side critical section. |
| 304 | */ |
Paul E. McKenney | 2a3fa84 | 2012-05-21 11:58:36 -0700 | [diff] [blame] | 305 | void rcu_read_unlock_special(struct task_struct *t) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 306 | { |
| 307 | int empty; |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 308 | int empty_exp; |
Paul E. McKenney | 389abd4 | 2011-09-21 14:41:37 -0700 | [diff] [blame] | 309 | int empty_exp_now; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 310 | unsigned long flags; |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 311 | struct list_head *np; |
Paul E. McKenney | 82e78d8 | 2011-08-04 07:55:34 -0700 | [diff] [blame] | 312 | #ifdef CONFIG_RCU_BOOST |
| 313 | struct rt_mutex *rbmp = NULL; |
| 314 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 315 | struct rcu_node *rnp; |
| 316 | int special; |
| 317 | |
| 318 | /* NMI handlers cannot block and cannot safely manipulate state. */ |
| 319 | if (in_nmi()) |
| 320 | return; |
| 321 | |
| 322 | local_irq_save(flags); |
| 323 | |
| 324 | /* |
| 325 | * If RCU core is waiting for this CPU to exit critical section, |
| 326 | * let it know that we have done so. |
| 327 | */ |
| 328 | special = t->rcu_read_unlock_special; |
| 329 | if (special & RCU_READ_UNLOCK_NEED_QS) { |
Paul E. McKenney | c3422be | 2009-09-13 09:15:10 -0700 | [diff] [blame] | 330 | rcu_preempt_qs(smp_processor_id()); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 331 | } |
| 332 | |
| 333 | /* Hardware IRQ handlers cannot block. */ |
Peter Zijlstra | ec433f0 | 2011-07-19 15:32:00 -0700 | [diff] [blame] | 334 | if (in_irq() || in_serving_softirq()) { |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 335 | local_irq_restore(flags); |
| 336 | return; |
| 337 | } |
| 338 | |
| 339 | /* Clean up if blocked during RCU read-side critical section. */ |
| 340 | if (special & RCU_READ_UNLOCK_BLOCKED) { |
| 341 | t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED; |
| 342 | |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 343 | /* |
| 344 | * Remove this task from the list it blocked on. The |
| 345 | * task can migrate while we acquire the lock, but at |
| 346 | * most one time. So at most two passes through loop. |
| 347 | */ |
| 348 | for (;;) { |
Paul E. McKenney | 8684896 | 2009-08-27 15:00:12 -0700 | [diff] [blame] | 349 | rnp = t->rcu_blocked_node; |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 350 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
Paul E. McKenney | 8684896 | 2009-08-27 15:00:12 -0700 | [diff] [blame] | 351 | if (rnp == t->rcu_blocked_node) |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 352 | break; |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 353 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 354 | } |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 355 | empty = !rcu_preempt_blocked_readers_cgp(rnp); |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 356 | empty_exp = !rcu_preempted_readers_exp(rnp); |
| 357 | smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */ |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 358 | np = rcu_next_node_entry(t, rnp); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 359 | list_del_init(&t->rcu_node_entry); |
Paul E. McKenney | 82e78d8 | 2011-08-04 07:55:34 -0700 | [diff] [blame] | 360 | t->rcu_blocked_node = NULL; |
Paul E. McKenney | d4c08f2 | 2011-06-25 06:36:56 -0700 | [diff] [blame] | 361 | trace_rcu_unlock_preempted_task("rcu_preempt", |
| 362 | rnp->gpnum, t->pid); |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 363 | if (&t->rcu_node_entry == rnp->gp_tasks) |
| 364 | rnp->gp_tasks = np; |
| 365 | if (&t->rcu_node_entry == rnp->exp_tasks) |
| 366 | rnp->exp_tasks = np; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 367 | #ifdef CONFIG_RCU_BOOST |
| 368 | if (&t->rcu_node_entry == rnp->boost_tasks) |
| 369 | rnp->boost_tasks = np; |
Paul E. McKenney | 82e78d8 | 2011-08-04 07:55:34 -0700 | [diff] [blame] | 370 | /* Snapshot/clear ->rcu_boost_mutex with rcu_node lock held. */ |
| 371 | if (t->rcu_boost_mutex) { |
| 372 | rbmp = t->rcu_boost_mutex; |
| 373 | t->rcu_boost_mutex = NULL; |
Paul E. McKenney | 7765be2 | 2011-07-14 12:24:11 -0700 | [diff] [blame] | 374 | } |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 375 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 376 | |
| 377 | /* |
| 378 | * If this was the last task on the current list, and if |
| 379 | * we aren't waiting on any CPUs, report the quiescent state. |
Paul E. McKenney | 389abd4 | 2011-09-21 14:41:37 -0700 | [diff] [blame] | 380 | * Note that rcu_report_unblock_qs_rnp() releases rnp->lock, |
| 381 | * so we must take a snapshot of the expedited state. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 382 | */ |
Paul E. McKenney | 389abd4 | 2011-09-21 14:41:37 -0700 | [diff] [blame] | 383 | empty_exp_now = !rcu_preempted_readers_exp(rnp); |
Paul E. McKenney | d4c08f2 | 2011-06-25 06:36:56 -0700 | [diff] [blame] | 384 | if (!empty && !rcu_preempt_blocked_readers_cgp(rnp)) { |
| 385 | trace_rcu_quiescent_state_report("preempt_rcu", |
| 386 | rnp->gpnum, |
| 387 | 0, rnp->qsmask, |
| 388 | rnp->level, |
| 389 | rnp->grplo, |
| 390 | rnp->grphi, |
| 391 | !!rnp->gp_tasks); |
Paul E. McKenney | d3f6bad | 2009-12-02 12:10:13 -0800 | [diff] [blame] | 392 | rcu_report_unblock_qs_rnp(rnp, flags); |
Paul E. McKenney | c701d5d | 2012-06-28 08:08:25 -0700 | [diff] [blame] | 393 | } else { |
Paul E. McKenney | d4c08f2 | 2011-06-25 06:36:56 -0700 | [diff] [blame] | 394 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | c701d5d | 2012-06-28 08:08:25 -0700 | [diff] [blame] | 395 | } |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 396 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 397 | #ifdef CONFIG_RCU_BOOST |
| 398 | /* Unboost if we were boosted. */ |
Paul E. McKenney | 82e78d8 | 2011-08-04 07:55:34 -0700 | [diff] [blame] | 399 | if (rbmp) |
| 400 | rt_mutex_unlock(rbmp); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 401 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
| 402 | |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 403 | /* |
| 404 | * If this was the last task on the expedited lists, |
| 405 | * then we need to report up the rcu_node hierarchy. |
| 406 | */ |
Paul E. McKenney | 389abd4 | 2011-09-21 14:41:37 -0700 | [diff] [blame] | 407 | if (!empty_exp && empty_exp_now) |
Thomas Gleixner | b40d293 | 2011-10-22 07:12:34 -0700 | [diff] [blame] | 408 | rcu_report_exp_rnp(&rcu_preempt_state, rnp, true); |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 409 | } else { |
| 410 | local_irq_restore(flags); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 411 | } |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 412 | } |
| 413 | |
Paul E. McKenney | 1ed509a | 2010-02-22 17:05:05 -0800 | [diff] [blame] | 414 | #ifdef CONFIG_RCU_CPU_STALL_VERBOSE |
| 415 | |
| 416 | /* |
| 417 | * Dump detailed information for all tasks blocking the current RCU |
| 418 | * grace period on the specified rcu_node structure. |
| 419 | */ |
| 420 | static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp) |
| 421 | { |
| 422 | unsigned long flags; |
Paul E. McKenney | 1ed509a | 2010-02-22 17:05:05 -0800 | [diff] [blame] | 423 | struct task_struct *t; |
| 424 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 425 | if (!rcu_preempt_blocked_readers_cgp(rnp)) |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 426 | return; |
| 427 | raw_spin_lock_irqsave(&rnp->lock, flags); |
| 428 | t = list_entry(rnp->gp_tasks, |
| 429 | struct task_struct, rcu_node_entry); |
| 430 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) |
| 431 | sched_show_task(t); |
| 432 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | 1ed509a | 2010-02-22 17:05:05 -0800 | [diff] [blame] | 433 | } |
| 434 | |
| 435 | /* |
| 436 | * Dump detailed information for all tasks blocking the current RCU |
| 437 | * grace period. |
| 438 | */ |
| 439 | static void rcu_print_detail_task_stall(struct rcu_state *rsp) |
| 440 | { |
| 441 | struct rcu_node *rnp = rcu_get_root(rsp); |
| 442 | |
| 443 | rcu_print_detail_task_stall_rnp(rnp); |
| 444 | rcu_for_each_leaf_node(rsp, rnp) |
| 445 | rcu_print_detail_task_stall_rnp(rnp); |
| 446 | } |
| 447 | |
| 448 | #else /* #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */ |
| 449 | |
| 450 | static void rcu_print_detail_task_stall(struct rcu_state *rsp) |
| 451 | { |
| 452 | } |
| 453 | |
| 454 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_VERBOSE */ |
| 455 | |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 456 | #ifdef CONFIG_RCU_CPU_STALL_INFO |
| 457 | |
| 458 | static void rcu_print_task_stall_begin(struct rcu_node *rnp) |
| 459 | { |
| 460 | printk(KERN_ERR "\tTasks blocked on level-%d rcu_node (CPUs %d-%d):", |
| 461 | rnp->level, rnp->grplo, rnp->grphi); |
| 462 | } |
| 463 | |
| 464 | static void rcu_print_task_stall_end(void) |
| 465 | { |
| 466 | printk(KERN_CONT "\n"); |
| 467 | } |
| 468 | |
| 469 | #else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ |
| 470 | |
| 471 | static void rcu_print_task_stall_begin(struct rcu_node *rnp) |
| 472 | { |
| 473 | } |
| 474 | |
| 475 | static void rcu_print_task_stall_end(void) |
| 476 | { |
| 477 | } |
| 478 | |
| 479 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */ |
| 480 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 481 | /* |
| 482 | * Scan the current list of tasks blocked within RCU read-side critical |
| 483 | * sections, printing out the tid of each. |
| 484 | */ |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 485 | static int rcu_print_task_stall(struct rcu_node *rnp) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 486 | { |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 487 | struct task_struct *t; |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 488 | int ndetected = 0; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 489 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 490 | if (!rcu_preempt_blocked_readers_cgp(rnp)) |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 491 | return 0; |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 492 | rcu_print_task_stall_begin(rnp); |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 493 | t = list_entry(rnp->gp_tasks, |
| 494 | struct task_struct, rcu_node_entry); |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 495 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 496 | printk(KERN_CONT " P%d", t->pid); |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 497 | ndetected++; |
| 498 | } |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 499 | rcu_print_task_stall_end(); |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 500 | return ndetected; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 501 | } |
| 502 | |
Paul E. McKenney | 53d84e0 | 2010-08-10 14:28:53 -0700 | [diff] [blame] | 503 | /* |
Paul E. McKenney | b0e165c | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 504 | * Check that the list of blocked tasks for the newly completed grace |
| 505 | * period is in fact empty. It is a serious bug to complete a grace |
| 506 | * period that still has RCU readers blocked! This function must be |
| 507 | * invoked -before- updating this rnp's ->gpnum, and the rnp's ->lock |
| 508 | * must be held by the caller. |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 509 | * |
| 510 | * Also, if there are blocked tasks on the list, they automatically |
| 511 | * block the newly created grace period, so set up ->gp_tasks accordingly. |
Paul E. McKenney | b0e165c | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 512 | */ |
| 513 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) |
| 514 | { |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 515 | WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 516 | if (!list_empty(&rnp->blkd_tasks)) |
| 517 | rnp->gp_tasks = rnp->blkd_tasks.next; |
Paul E. McKenney | 28ecd58 | 2009-09-18 09:50:17 -0700 | [diff] [blame] | 518 | WARN_ON_ONCE(rnp->qsmask); |
Paul E. McKenney | b0e165c | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 519 | } |
| 520 | |
Paul E. McKenney | 33f7614 | 2009-08-24 09:42:01 -0700 | [diff] [blame] | 521 | #ifdef CONFIG_HOTPLUG_CPU |
| 522 | |
| 523 | /* |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 524 | * Handle tasklist migration for case in which all CPUs covered by the |
| 525 | * specified rcu_node have gone offline. Move them up to the root |
| 526 | * rcu_node. The reason for not just moving them to the immediate |
| 527 | * parent is to remove the need for rcu_read_unlock_special() to |
| 528 | * make more than two attempts to acquire the target rcu_node's lock. |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 529 | * Returns true if there were tasks blocking the current RCU grace |
| 530 | * period. |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 531 | * |
Paul E. McKenney | 237c80c | 2009-10-15 09:26:14 -0700 | [diff] [blame] | 532 | * Returns 1 if there was previously a task blocking the current grace |
| 533 | * period on the specified rcu_node structure. |
| 534 | * |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 535 | * The caller must hold rnp->lock with irqs disabled. |
| 536 | */ |
Paul E. McKenney | 237c80c | 2009-10-15 09:26:14 -0700 | [diff] [blame] | 537 | static int rcu_preempt_offline_tasks(struct rcu_state *rsp, |
| 538 | struct rcu_node *rnp, |
| 539 | struct rcu_data *rdp) |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 540 | { |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 541 | struct list_head *lp; |
| 542 | struct list_head *lp_root; |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 543 | int retval = 0; |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 544 | struct rcu_node *rnp_root = rcu_get_root(rsp); |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 545 | struct task_struct *t; |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 546 | |
Paul E. McKenney | 8684896 | 2009-08-27 15:00:12 -0700 | [diff] [blame] | 547 | if (rnp == rnp_root) { |
| 548 | WARN_ONCE(1, "Last CPU thought to be offlined?"); |
Paul E. McKenney | 237c80c | 2009-10-15 09:26:14 -0700 | [diff] [blame] | 549 | return 0; /* Shouldn't happen: at least one CPU online. */ |
Paul E. McKenney | 8684896 | 2009-08-27 15:00:12 -0700 | [diff] [blame] | 550 | } |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 551 | |
| 552 | /* If we are on an internal node, complain bitterly. */ |
| 553 | WARN_ON_ONCE(rnp != rdp->mynode); |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 554 | |
| 555 | /* |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 556 | * Move tasks up to root rcu_node. Don't try to get fancy for |
| 557 | * this corner-case operation -- just put this node's tasks |
| 558 | * at the head of the root node's list, and update the root node's |
| 559 | * ->gp_tasks and ->exp_tasks pointers to those of this node's, |
| 560 | * if non-NULL. This might result in waiting for more tasks than |
| 561 | * absolutely necessary, but this is a good performance/complexity |
| 562 | * tradeoff. |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 563 | */ |
Paul E. McKenney | 2036d94 | 2012-01-30 17:02:47 -0800 | [diff] [blame] | 564 | if (rcu_preempt_blocked_readers_cgp(rnp) && rnp->qsmask == 0) |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 565 | retval |= RCU_OFL_TASKS_NORM_GP; |
| 566 | if (rcu_preempted_readers_exp(rnp)) |
| 567 | retval |= RCU_OFL_TASKS_EXP_GP; |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 568 | lp = &rnp->blkd_tasks; |
| 569 | lp_root = &rnp_root->blkd_tasks; |
| 570 | while (!list_empty(lp)) { |
| 571 | t = list_entry(lp->next, typeof(*t), rcu_node_entry); |
| 572 | raw_spin_lock(&rnp_root->lock); /* irqs already disabled */ |
| 573 | list_del(&t->rcu_node_entry); |
| 574 | t->rcu_blocked_node = rnp_root; |
| 575 | list_add(&t->rcu_node_entry, lp_root); |
| 576 | if (&t->rcu_node_entry == rnp->gp_tasks) |
| 577 | rnp_root->gp_tasks = rnp->gp_tasks; |
| 578 | if (&t->rcu_node_entry == rnp->exp_tasks) |
| 579 | rnp_root->exp_tasks = rnp->exp_tasks; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 580 | #ifdef CONFIG_RCU_BOOST |
| 581 | if (&t->rcu_node_entry == rnp->boost_tasks) |
| 582 | rnp_root->boost_tasks = rnp->boost_tasks; |
| 583 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 584 | raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */ |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 585 | } |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 586 | |
| 587 | #ifdef CONFIG_RCU_BOOST |
| 588 | /* In case root is being boosted and leaf is not. */ |
| 589 | raw_spin_lock(&rnp_root->lock); /* irqs already disabled */ |
| 590 | if (rnp_root->boost_tasks != NULL && |
| 591 | rnp_root->boost_tasks != rnp_root->gp_tasks) |
| 592 | rnp_root->boost_tasks = rnp_root->gp_tasks; |
| 593 | raw_spin_unlock(&rnp_root->lock); /* irqs still disabled */ |
| 594 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
| 595 | |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 596 | rnp->gp_tasks = NULL; |
| 597 | rnp->exp_tasks = NULL; |
Paul E. McKenney | 237c80c | 2009-10-15 09:26:14 -0700 | [diff] [blame] | 598 | return retval; |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 599 | } |
| 600 | |
Paul E. McKenney | e560140 | 2012-01-07 11:03:57 -0800 | [diff] [blame] | 601 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
| 602 | |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 603 | /* |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 604 | * Check for a quiescent state from the current CPU. When a task blocks, |
| 605 | * the task is recorded in the corresponding CPU's rcu_node structure, |
| 606 | * which is checked elsewhere. |
| 607 | * |
| 608 | * Caller must disable hard irqs. |
| 609 | */ |
| 610 | static void rcu_preempt_check_callbacks(int cpu) |
| 611 | { |
| 612 | struct task_struct *t = current; |
| 613 | |
| 614 | if (t->rcu_read_lock_nesting == 0) { |
Paul E. McKenney | c3422be | 2009-09-13 09:15:10 -0700 | [diff] [blame] | 615 | rcu_preempt_qs(cpu); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 616 | return; |
| 617 | } |
Paul E. McKenney | 10f39bb | 2011-07-17 21:14:35 -0700 | [diff] [blame] | 618 | if (t->rcu_read_lock_nesting > 0 && |
| 619 | per_cpu(rcu_preempt_data, cpu).qs_pending) |
Paul E. McKenney | c3422be | 2009-09-13 09:15:10 -0700 | [diff] [blame] | 620 | t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 621 | } |
| 622 | |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 623 | #ifdef CONFIG_RCU_BOOST |
| 624 | |
Shaohua Li | 0922337 | 2011-06-14 13:26:25 +0800 | [diff] [blame] | 625 | static void rcu_preempt_do_callbacks(void) |
| 626 | { |
| 627 | rcu_do_batch(&rcu_preempt_state, &__get_cpu_var(rcu_preempt_data)); |
| 628 | } |
| 629 | |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 630 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
| 631 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 632 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 633 | * Queue a preemptible-RCU callback for invocation after a grace period. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 634 | */ |
| 635 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
| 636 | { |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 637 | __call_rcu(head, func, &rcu_preempt_state, 0); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 638 | } |
| 639 | EXPORT_SYMBOL_GPL(call_rcu); |
| 640 | |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 641 | /* |
| 642 | * Queue an RCU callback for lazy invocation after a grace period. |
| 643 | * This will likely be later named something like "call_rcu_lazy()", |
| 644 | * but this change will require some way of tagging the lazy RCU |
| 645 | * callbacks in the list of pending callbacks. Until then, this |
| 646 | * function may only be called from __kfree_rcu(). |
| 647 | */ |
| 648 | void kfree_call_rcu(struct rcu_head *head, |
| 649 | void (*func)(struct rcu_head *rcu)) |
| 650 | { |
| 651 | __call_rcu(head, func, &rcu_preempt_state, 1); |
| 652 | } |
| 653 | EXPORT_SYMBOL_GPL(kfree_call_rcu); |
| 654 | |
Paul E. McKenney | 6ebb237 | 2009-11-22 08:53:50 -0800 | [diff] [blame] | 655 | /** |
| 656 | * synchronize_rcu - wait until a grace period has elapsed. |
| 657 | * |
| 658 | * Control will return to the caller some time after a full grace |
| 659 | * period has elapsed, in other words after all currently executing RCU |
Paul E. McKenney | 77d8485 | 2010-07-08 17:38:59 -0700 | [diff] [blame] | 660 | * read-side critical sections have completed. Note, however, that |
| 661 | * upon return from synchronize_rcu(), the caller might well be executing |
| 662 | * concurrently with new RCU read-side critical sections that began while |
| 663 | * synchronize_rcu() was waiting. RCU read-side critical sections are |
| 664 | * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. |
Paul E. McKenney | 6ebb237 | 2009-11-22 08:53:50 -0800 | [diff] [blame] | 665 | */ |
| 666 | void synchronize_rcu(void) |
| 667 | { |
Paul E. McKenney | fe15d70 | 2012-01-04 13:30:33 -0800 | [diff] [blame] | 668 | rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
| 669 | !lock_is_held(&rcu_lock_map) && |
| 670 | !lock_is_held(&rcu_sched_lock_map), |
| 671 | "Illegal synchronize_rcu() in RCU read-side critical section"); |
Paul E. McKenney | 6ebb237 | 2009-11-22 08:53:50 -0800 | [diff] [blame] | 672 | if (!rcu_scheduler_active) |
| 673 | return; |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 674 | wait_rcu_gp(call_rcu); |
Paul E. McKenney | 6ebb237 | 2009-11-22 08:53:50 -0800 | [diff] [blame] | 675 | } |
| 676 | EXPORT_SYMBOL_GPL(synchronize_rcu); |
| 677 | |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 678 | static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq); |
| 679 | static long sync_rcu_preempt_exp_count; |
| 680 | static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex); |
| 681 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 682 | /* |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 683 | * Return non-zero if there are any tasks in RCU read-side critical |
| 684 | * sections blocking the current preemptible-RCU expedited grace period. |
| 685 | * If there is no preemptible-RCU expedited grace period currently in |
| 686 | * progress, returns zero unconditionally. |
| 687 | */ |
| 688 | static int rcu_preempted_readers_exp(struct rcu_node *rnp) |
| 689 | { |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 690 | return rnp->exp_tasks != NULL; |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 691 | } |
| 692 | |
| 693 | /* |
| 694 | * return non-zero if there is no RCU expedited grace period in progress |
| 695 | * for the specified rcu_node structure, in other words, if all CPUs and |
| 696 | * tasks covered by the specified rcu_node structure have done their bit |
| 697 | * for the current expedited grace period. Works only for preemptible |
| 698 | * RCU -- other RCU implementation use other means. |
| 699 | * |
| 700 | * Caller must hold sync_rcu_preempt_exp_mutex. |
| 701 | */ |
| 702 | static int sync_rcu_preempt_exp_done(struct rcu_node *rnp) |
| 703 | { |
| 704 | return !rcu_preempted_readers_exp(rnp) && |
| 705 | ACCESS_ONCE(rnp->expmask) == 0; |
| 706 | } |
| 707 | |
| 708 | /* |
| 709 | * Report the exit from RCU read-side critical section for the last task |
| 710 | * that queued itself during or before the current expedited preemptible-RCU |
| 711 | * grace period. This event is reported either to the rcu_node structure on |
| 712 | * which the task was queued or to one of that rcu_node structure's ancestors, |
| 713 | * recursively up the tree. (Calm down, calm down, we do the recursion |
| 714 | * iteratively!) |
| 715 | * |
Thomas Gleixner | b40d293 | 2011-10-22 07:12:34 -0700 | [diff] [blame] | 716 | * Most callers will set the "wake" flag, but the task initiating the |
| 717 | * expedited grace period need not wake itself. |
| 718 | * |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 719 | * Caller must hold sync_rcu_preempt_exp_mutex. |
| 720 | */ |
Thomas Gleixner | b40d293 | 2011-10-22 07:12:34 -0700 | [diff] [blame] | 721 | static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, |
| 722 | bool wake) |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 723 | { |
| 724 | unsigned long flags; |
| 725 | unsigned long mask; |
| 726 | |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 727 | raw_spin_lock_irqsave(&rnp->lock, flags); |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 728 | for (;;) { |
Paul E. McKenney | 131906b | 2011-07-17 02:05:49 -0700 | [diff] [blame] | 729 | if (!sync_rcu_preempt_exp_done(rnp)) { |
| 730 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 731 | break; |
Paul E. McKenney | 131906b | 2011-07-17 02:05:49 -0700 | [diff] [blame] | 732 | } |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 733 | if (rnp->parent == NULL) { |
Paul E. McKenney | 131906b | 2011-07-17 02:05:49 -0700 | [diff] [blame] | 734 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Thomas Gleixner | b40d293 | 2011-10-22 07:12:34 -0700 | [diff] [blame] | 735 | if (wake) |
| 736 | wake_up(&sync_rcu_preempt_exp_wq); |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 737 | break; |
| 738 | } |
| 739 | mask = rnp->grpmask; |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 740 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 741 | rnp = rnp->parent; |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 742 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 743 | rnp->expmask &= ~mask; |
| 744 | } |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 745 | } |
| 746 | |
| 747 | /* |
| 748 | * Snapshot the tasks blocking the newly started preemptible-RCU expedited |
| 749 | * grace period for the specified rcu_node structure. If there are no such |
| 750 | * tasks, report it up the rcu_node hierarchy. |
| 751 | * |
| 752 | * Caller must hold sync_rcu_preempt_exp_mutex and rsp->onofflock. |
| 753 | */ |
| 754 | static void |
| 755 | sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp) |
| 756 | { |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 757 | unsigned long flags; |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 758 | int must_wait = 0; |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 759 | |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 760 | raw_spin_lock_irqsave(&rnp->lock, flags); |
Paul E. McKenney | c701d5d | 2012-06-28 08:08:25 -0700 | [diff] [blame] | 761 | if (list_empty(&rnp->blkd_tasks)) { |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 762 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | c701d5d | 2012-06-28 08:08:25 -0700 | [diff] [blame] | 763 | } else { |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 764 | rnp->exp_tasks = rnp->blkd_tasks.next; |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 765 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock */ |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 766 | must_wait = 1; |
| 767 | } |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 768 | if (!must_wait) |
Thomas Gleixner | b40d293 | 2011-10-22 07:12:34 -0700 | [diff] [blame] | 769 | rcu_report_exp_rnp(rsp, rnp, false); /* Don't wake self. */ |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 770 | } |
| 771 | |
Paul E. McKenney | 236fefa | 2012-01-31 14:00:41 -0800 | [diff] [blame] | 772 | /** |
| 773 | * synchronize_rcu_expedited - Brute-force RCU grace period |
| 774 | * |
| 775 | * Wait for an RCU-preempt grace period, but expedite it. The basic |
| 776 | * idea is to invoke synchronize_sched_expedited() to push all the tasks to |
| 777 | * the ->blkd_tasks lists and wait for this list to drain. This consumes |
| 778 | * significant time on all CPUs and is unfriendly to real-time workloads, |
| 779 | * so is thus not recommended for any sort of common-case code. |
| 780 | * In fact, if you are using synchronize_rcu_expedited() in a loop, |
| 781 | * please restructure your code to batch your updates, and then Use a |
| 782 | * single synchronize_rcu() instead. |
| 783 | * |
| 784 | * Note that it is illegal to call this function while holding any lock |
| 785 | * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal |
| 786 | * to call this function from a CPU-hotplug notifier. Failing to observe |
| 787 | * these restriction will result in deadlock. |
Paul E. McKenney | 019129d5 | 2009-10-14 10:15:56 -0700 | [diff] [blame] | 788 | */ |
| 789 | void synchronize_rcu_expedited(void) |
| 790 | { |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 791 | unsigned long flags; |
| 792 | struct rcu_node *rnp; |
| 793 | struct rcu_state *rsp = &rcu_preempt_state; |
| 794 | long snap; |
| 795 | int trycount = 0; |
| 796 | |
| 797 | smp_mb(); /* Caller's modifications seen first by other CPUs. */ |
| 798 | snap = ACCESS_ONCE(sync_rcu_preempt_exp_count) + 1; |
| 799 | smp_mb(); /* Above access cannot bleed into critical section. */ |
| 800 | |
| 801 | /* |
| 802 | * Acquire lock, falling back to synchronize_rcu() if too many |
| 803 | * lock-acquisition failures. Of course, if someone does the |
| 804 | * expedited grace period for us, just leave. |
| 805 | */ |
| 806 | while (!mutex_trylock(&sync_rcu_preempt_exp_mutex)) { |
Paul E. McKenney | c701d5d | 2012-06-28 08:08:25 -0700 | [diff] [blame] | 807 | if (trycount++ < 10) { |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 808 | udelay(trycount * num_online_cpus()); |
Paul E. McKenney | c701d5d | 2012-06-28 08:08:25 -0700 | [diff] [blame] | 809 | } else { |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 810 | synchronize_rcu(); |
| 811 | return; |
| 812 | } |
| 813 | if ((ACCESS_ONCE(sync_rcu_preempt_exp_count) - snap) > 0) |
| 814 | goto mb_ret; /* Others did our work for us. */ |
| 815 | } |
| 816 | if ((ACCESS_ONCE(sync_rcu_preempt_exp_count) - snap) > 0) |
| 817 | goto unlock_mb_ret; /* Others did our work for us. */ |
| 818 | |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 819 | /* force all RCU readers onto ->blkd_tasks lists. */ |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 820 | synchronize_sched_expedited(); |
| 821 | |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 822 | raw_spin_lock_irqsave(&rsp->onofflock, flags); |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 823 | |
| 824 | /* Initialize ->expmask for all non-leaf rcu_node structures. */ |
| 825 | rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) { |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 826 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 827 | rnp->expmask = rnp->qsmaskinit; |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 828 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 829 | } |
| 830 | |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 831 | /* Snapshot current state of ->blkd_tasks lists. */ |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 832 | rcu_for_each_leaf_node(rsp, rnp) |
| 833 | sync_rcu_preempt_exp_init(rsp, rnp); |
| 834 | if (NUM_RCU_NODES > 1) |
| 835 | sync_rcu_preempt_exp_init(rsp, rcu_get_root(rsp)); |
| 836 | |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 837 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 838 | |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 839 | /* Wait for snapshotted ->blkd_tasks lists to drain. */ |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 840 | rnp = rcu_get_root(rsp); |
| 841 | wait_event(sync_rcu_preempt_exp_wq, |
| 842 | sync_rcu_preempt_exp_done(rnp)); |
| 843 | |
| 844 | /* Clean up and exit. */ |
| 845 | smp_mb(); /* ensure expedited GP seen before counter increment. */ |
| 846 | ACCESS_ONCE(sync_rcu_preempt_exp_count)++; |
| 847 | unlock_mb_ret: |
| 848 | mutex_unlock(&sync_rcu_preempt_exp_mutex); |
| 849 | mb_ret: |
| 850 | smp_mb(); /* ensure subsequent action seen after grace period. */ |
Paul E. McKenney | 019129d5 | 2009-10-14 10:15:56 -0700 | [diff] [blame] | 851 | } |
| 852 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); |
| 853 | |
Paul E. McKenney | e74f4c4 | 2009-10-06 21:48:17 -0700 | [diff] [blame] | 854 | /** |
| 855 | * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. |
| 856 | */ |
| 857 | void rcu_barrier(void) |
| 858 | { |
Paul E. McKenney | 037b64e | 2012-05-28 23:26:01 -0700 | [diff] [blame] | 859 | _rcu_barrier(&rcu_preempt_state); |
Paul E. McKenney | e74f4c4 | 2009-10-06 21:48:17 -0700 | [diff] [blame] | 860 | } |
| 861 | EXPORT_SYMBOL_GPL(rcu_barrier); |
| 862 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 863 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 864 | * Initialize preemptible RCU's state structures. |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 865 | */ |
| 866 | static void __init __rcu_init_preempt(void) |
| 867 | { |
Lai Jiangshan | 394f99a | 2010-06-28 16:25:04 +0800 | [diff] [blame] | 868 | rcu_init_one(&rcu_preempt_state, &rcu_preempt_data); |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 869 | } |
| 870 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 871 | #else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ |
| 872 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 873 | static struct rcu_state *rcu_state = &rcu_sched_state; |
| 874 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 875 | /* |
| 876 | * Tell them what RCU they are running. |
| 877 | */ |
Paul E. McKenney | 0e0fc1c | 2009-11-11 11:28:06 -0800 | [diff] [blame] | 878 | static void __init rcu_bootup_announce(void) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 879 | { |
| 880 | printk(KERN_INFO "Hierarchical RCU implementation.\n"); |
Paul E. McKenney | 26845c2 | 2010-04-13 14:19:23 -0700 | [diff] [blame] | 881 | rcu_bootup_announce_oddness(); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 882 | } |
| 883 | |
| 884 | /* |
| 885 | * Return the number of RCU batches processed thus far for debug & stats. |
| 886 | */ |
| 887 | long rcu_batches_completed(void) |
| 888 | { |
| 889 | return rcu_batches_completed_sched(); |
| 890 | } |
| 891 | EXPORT_SYMBOL_GPL(rcu_batches_completed); |
| 892 | |
| 893 | /* |
Paul E. McKenney | bf66f18 | 2010-01-04 15:09:10 -0800 | [diff] [blame] | 894 | * Force a quiescent state for RCU, which, because there is no preemptible |
| 895 | * RCU, becomes the same as rcu-sched. |
| 896 | */ |
| 897 | void rcu_force_quiescent_state(void) |
| 898 | { |
| 899 | rcu_sched_force_quiescent_state(); |
| 900 | } |
| 901 | EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); |
| 902 | |
| 903 | /* |
Paul E. McKenney | cba6d0d | 2012-07-02 07:08:42 -0700 | [diff] [blame] | 904 | * Because preemptible RCU does not exist, we never have to check for |
| 905 | * CPUs being in quiescent states. |
| 906 | */ |
| 907 | static void rcu_preempt_note_context_switch(int cpu) |
| 908 | { |
| 909 | } |
| 910 | |
| 911 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 912 | * Because preemptible RCU does not exist, there are never any preempted |
Paul E. McKenney | fc2219d | 2009-09-23 09:50:41 -0700 | [diff] [blame] | 913 | * RCU readers. |
| 914 | */ |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 915 | static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) |
Paul E. McKenney | fc2219d | 2009-09-23 09:50:41 -0700 | [diff] [blame] | 916 | { |
| 917 | return 0; |
| 918 | } |
| 919 | |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 920 | #ifdef CONFIG_HOTPLUG_CPU |
| 921 | |
| 922 | /* Because preemptible RCU does not exist, no quieting of tasks. */ |
Paul E. McKenney | d3f6bad | 2009-12-02 12:10:13 -0800 | [diff] [blame] | 923 | static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags) |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 924 | { |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 925 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 926 | } |
| 927 | |
| 928 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
| 929 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 930 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 931 | * Because preemptible RCU does not exist, we never have to check for |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 932 | * tasks blocked within RCU read-side critical sections. |
| 933 | */ |
Paul E. McKenney | 1ed509a | 2010-02-22 17:05:05 -0800 | [diff] [blame] | 934 | static void rcu_print_detail_task_stall(struct rcu_state *rsp) |
| 935 | { |
| 936 | } |
| 937 | |
| 938 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 939 | * Because preemptible RCU does not exist, we never have to check for |
Paul E. McKenney | 1ed509a | 2010-02-22 17:05:05 -0800 | [diff] [blame] | 940 | * tasks blocked within RCU read-side critical sections. |
| 941 | */ |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 942 | static int rcu_print_task_stall(struct rcu_node *rnp) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 943 | { |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 944 | return 0; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 945 | } |
| 946 | |
Paul E. McKenney | 53d84e0 | 2010-08-10 14:28:53 -0700 | [diff] [blame] | 947 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 948 | * Because there is no preemptible RCU, there can be no readers blocked, |
Paul E. McKenney | 49e2912 | 2009-09-18 09:50:19 -0700 | [diff] [blame] | 949 | * so there is no need to check for blocked tasks. So check only for |
| 950 | * bogus qsmask values. |
Paul E. McKenney | b0e165c | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 951 | */ |
| 952 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) |
| 953 | { |
Paul E. McKenney | 49e2912 | 2009-09-18 09:50:19 -0700 | [diff] [blame] | 954 | WARN_ON_ONCE(rnp->qsmask); |
Paul E. McKenney | b0e165c | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 955 | } |
| 956 | |
Paul E. McKenney | 33f7614 | 2009-08-24 09:42:01 -0700 | [diff] [blame] | 957 | #ifdef CONFIG_HOTPLUG_CPU |
| 958 | |
| 959 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 960 | * Because preemptible RCU does not exist, it never needs to migrate |
Paul E. McKenney | 237c80c | 2009-10-15 09:26:14 -0700 | [diff] [blame] | 961 | * tasks that were blocked within RCU read-side critical sections, and |
| 962 | * such non-existent tasks cannot possibly have been blocking the current |
| 963 | * grace period. |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 964 | */ |
Paul E. McKenney | 237c80c | 2009-10-15 09:26:14 -0700 | [diff] [blame] | 965 | static int rcu_preempt_offline_tasks(struct rcu_state *rsp, |
| 966 | struct rcu_node *rnp, |
| 967 | struct rcu_data *rdp) |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 968 | { |
Paul E. McKenney | 237c80c | 2009-10-15 09:26:14 -0700 | [diff] [blame] | 969 | return 0; |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 970 | } |
| 971 | |
Paul E. McKenney | e560140 | 2012-01-07 11:03:57 -0800 | [diff] [blame] | 972 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
| 973 | |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 974 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 975 | * Because preemptible RCU does not exist, it never has any callbacks |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 976 | * to check. |
| 977 | */ |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 978 | static void rcu_preempt_check_callbacks(int cpu) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 979 | { |
| 980 | } |
| 981 | |
| 982 | /* |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 983 | * Queue an RCU callback for lazy invocation after a grace period. |
| 984 | * This will likely be later named something like "call_rcu_lazy()", |
| 985 | * but this change will require some way of tagging the lazy RCU |
| 986 | * callbacks in the list of pending callbacks. Until then, this |
| 987 | * function may only be called from __kfree_rcu(). |
| 988 | * |
| 989 | * Because there is no preemptible RCU, we use RCU-sched instead. |
| 990 | */ |
| 991 | void kfree_call_rcu(struct rcu_head *head, |
| 992 | void (*func)(struct rcu_head *rcu)) |
| 993 | { |
| 994 | __call_rcu(head, func, &rcu_sched_state, 1); |
| 995 | } |
| 996 | EXPORT_SYMBOL_GPL(kfree_call_rcu); |
| 997 | |
| 998 | /* |
Paul E. McKenney | 019129d5 | 2009-10-14 10:15:56 -0700 | [diff] [blame] | 999 | * Wait for an rcu-preempt grace period, but make it happen quickly. |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 1000 | * But because preemptible RCU does not exist, map to rcu-sched. |
Paul E. McKenney | 019129d5 | 2009-10-14 10:15:56 -0700 | [diff] [blame] | 1001 | */ |
| 1002 | void synchronize_rcu_expedited(void) |
| 1003 | { |
| 1004 | synchronize_sched_expedited(); |
| 1005 | } |
| 1006 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); |
| 1007 | |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 1008 | #ifdef CONFIG_HOTPLUG_CPU |
| 1009 | |
| 1010 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 1011 | * Because preemptible RCU does not exist, there is never any need to |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 1012 | * report on tasks preempted in RCU read-side critical sections during |
| 1013 | * expedited RCU grace periods. |
| 1014 | */ |
Thomas Gleixner | b40d293 | 2011-10-22 07:12:34 -0700 | [diff] [blame] | 1015 | static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, |
| 1016 | bool wake) |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 1017 | { |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 1018 | } |
| 1019 | |
| 1020 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
| 1021 | |
Paul E. McKenney | 019129d5 | 2009-10-14 10:15:56 -0700 | [diff] [blame] | 1022 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 1023 | * Because preemptible RCU does not exist, rcu_barrier() is just |
Paul E. McKenney | e74f4c4 | 2009-10-06 21:48:17 -0700 | [diff] [blame] | 1024 | * another name for rcu_barrier_sched(). |
| 1025 | */ |
| 1026 | void rcu_barrier(void) |
| 1027 | { |
| 1028 | rcu_barrier_sched(); |
| 1029 | } |
| 1030 | EXPORT_SYMBOL_GPL(rcu_barrier); |
| 1031 | |
| 1032 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 1033 | * Because preemptible RCU does not exist, it need not be initialized. |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 1034 | */ |
| 1035 | static void __init __rcu_init_preempt(void) |
| 1036 | { |
| 1037 | } |
| 1038 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 1039 | #endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1040 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1041 | #ifdef CONFIG_RCU_BOOST |
| 1042 | |
| 1043 | #include "rtmutex_common.h" |
| 1044 | |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1045 | #ifdef CONFIG_RCU_TRACE |
| 1046 | |
| 1047 | static void rcu_initiate_boost_trace(struct rcu_node *rnp) |
| 1048 | { |
| 1049 | if (list_empty(&rnp->blkd_tasks)) |
| 1050 | rnp->n_balk_blkd_tasks++; |
| 1051 | else if (rnp->exp_tasks == NULL && rnp->gp_tasks == NULL) |
| 1052 | rnp->n_balk_exp_gp_tasks++; |
| 1053 | else if (rnp->gp_tasks != NULL && rnp->boost_tasks != NULL) |
| 1054 | rnp->n_balk_boost_tasks++; |
| 1055 | else if (rnp->gp_tasks != NULL && rnp->qsmask != 0) |
| 1056 | rnp->n_balk_notblocked++; |
| 1057 | else if (rnp->gp_tasks != NULL && |
Paul E. McKenney | a9f4793 | 2011-05-02 03:46:10 -0700 | [diff] [blame] | 1058 | ULONG_CMP_LT(jiffies, rnp->boost_time)) |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1059 | rnp->n_balk_notyet++; |
| 1060 | else |
| 1061 | rnp->n_balk_nos++; |
| 1062 | } |
| 1063 | |
| 1064 | #else /* #ifdef CONFIG_RCU_TRACE */ |
| 1065 | |
| 1066 | static void rcu_initiate_boost_trace(struct rcu_node *rnp) |
| 1067 | { |
| 1068 | } |
| 1069 | |
| 1070 | #endif /* #else #ifdef CONFIG_RCU_TRACE */ |
| 1071 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1072 | /* |
| 1073 | * Carry out RCU priority boosting on the task indicated by ->exp_tasks |
| 1074 | * or ->boost_tasks, advancing the pointer to the next task in the |
| 1075 | * ->blkd_tasks list. |
| 1076 | * |
| 1077 | * Note that irqs must be enabled: boosting the task can block. |
| 1078 | * Returns 1 if there are more tasks needing to be boosted. |
| 1079 | */ |
| 1080 | static int rcu_boost(struct rcu_node *rnp) |
| 1081 | { |
| 1082 | unsigned long flags; |
| 1083 | struct rt_mutex mtx; |
| 1084 | struct task_struct *t; |
| 1085 | struct list_head *tb; |
| 1086 | |
| 1087 | if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) |
| 1088 | return 0; /* Nothing left to boost. */ |
| 1089 | |
| 1090 | raw_spin_lock_irqsave(&rnp->lock, flags); |
| 1091 | |
| 1092 | /* |
| 1093 | * Recheck under the lock: all tasks in need of boosting |
| 1094 | * might exit their RCU read-side critical sections on their own. |
| 1095 | */ |
| 1096 | if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) { |
| 1097 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 1098 | return 0; |
| 1099 | } |
| 1100 | |
| 1101 | /* |
| 1102 | * Preferentially boost tasks blocking expedited grace periods. |
| 1103 | * This cannot starve the normal grace periods because a second |
| 1104 | * expedited grace period must boost all blocked tasks, including |
| 1105 | * those blocking the pre-existing normal grace period. |
| 1106 | */ |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1107 | if (rnp->exp_tasks != NULL) { |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1108 | tb = rnp->exp_tasks; |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1109 | rnp->n_exp_boosts++; |
| 1110 | } else { |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1111 | tb = rnp->boost_tasks; |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1112 | rnp->n_normal_boosts++; |
| 1113 | } |
| 1114 | rnp->n_tasks_boosted++; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1115 | |
| 1116 | /* |
| 1117 | * We boost task t by manufacturing an rt_mutex that appears to |
| 1118 | * be held by task t. We leave a pointer to that rt_mutex where |
| 1119 | * task t can find it, and task t will release the mutex when it |
| 1120 | * exits its outermost RCU read-side critical section. Then |
| 1121 | * simply acquiring this artificial rt_mutex will boost task |
| 1122 | * t's priority. (Thanks to tglx for suggesting this approach!) |
| 1123 | * |
| 1124 | * Note that task t must acquire rnp->lock to remove itself from |
| 1125 | * the ->blkd_tasks list, which it will do from exit() if from |
| 1126 | * nowhere else. We therefore are guaranteed that task t will |
| 1127 | * stay around at least until we drop rnp->lock. Note that |
| 1128 | * rnp->lock also resolves races between our priority boosting |
| 1129 | * and task t's exiting its outermost RCU read-side critical |
| 1130 | * section. |
| 1131 | */ |
| 1132 | t = container_of(tb, struct task_struct, rcu_node_entry); |
| 1133 | rt_mutex_init_proxy_locked(&mtx, t); |
| 1134 | t->rcu_boost_mutex = &mtx; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1135 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 1136 | rt_mutex_lock(&mtx); /* Side effect: boosts task t's priority. */ |
| 1137 | rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ |
| 1138 | |
Paul E. McKenney | 4f89b33 | 2011-12-09 14:43:47 -0800 | [diff] [blame] | 1139 | return ACCESS_ONCE(rnp->exp_tasks) != NULL || |
| 1140 | ACCESS_ONCE(rnp->boost_tasks) != NULL; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1141 | } |
| 1142 | |
| 1143 | /* |
| 1144 | * Timer handler to initiate waking up of boost kthreads that |
| 1145 | * have yielded the CPU due to excessive numbers of tasks to |
| 1146 | * boost. We wake up the per-rcu_node kthread, which in turn |
| 1147 | * will wake up the booster kthread. |
| 1148 | */ |
| 1149 | static void rcu_boost_kthread_timer(unsigned long arg) |
| 1150 | { |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1151 | invoke_rcu_node_kthread((struct rcu_node *)arg); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1152 | } |
| 1153 | |
| 1154 | /* |
| 1155 | * Priority-boosting kthread. One per leaf rcu_node and one for the |
| 1156 | * root rcu_node. |
| 1157 | */ |
| 1158 | static int rcu_boost_kthread(void *arg) |
| 1159 | { |
| 1160 | struct rcu_node *rnp = (struct rcu_node *)arg; |
| 1161 | int spincnt = 0; |
| 1162 | int more2boost; |
| 1163 | |
Paul E. McKenney | 385680a | 2011-06-21 22:43:26 -0700 | [diff] [blame] | 1164 | trace_rcu_utilization("Start boost kthread@init"); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1165 | for (;;) { |
Paul E. McKenney | d71df90 | 2011-03-29 17:48:28 -0700 | [diff] [blame] | 1166 | rnp->boost_kthread_status = RCU_KTHREAD_WAITING; |
Paul E. McKenney | 385680a | 2011-06-21 22:43:26 -0700 | [diff] [blame] | 1167 | trace_rcu_utilization("End boost kthread@rcu_wait"); |
Peter Zijlstra | 08bca60 | 2011-05-20 16:06:29 -0700 | [diff] [blame] | 1168 | rcu_wait(rnp->boost_tasks || rnp->exp_tasks); |
Paul E. McKenney | 385680a | 2011-06-21 22:43:26 -0700 | [diff] [blame] | 1169 | trace_rcu_utilization("Start boost kthread@rcu_wait"); |
Paul E. McKenney | d71df90 | 2011-03-29 17:48:28 -0700 | [diff] [blame] | 1170 | rnp->boost_kthread_status = RCU_KTHREAD_RUNNING; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1171 | more2boost = rcu_boost(rnp); |
| 1172 | if (more2boost) |
| 1173 | spincnt++; |
| 1174 | else |
| 1175 | spincnt = 0; |
| 1176 | if (spincnt > 10) { |
Paul E. McKenney | 385680a | 2011-06-21 22:43:26 -0700 | [diff] [blame] | 1177 | trace_rcu_utilization("End boost kthread@rcu_yield"); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1178 | rcu_yield(rcu_boost_kthread_timer, (unsigned long)rnp); |
Paul E. McKenney | 385680a | 2011-06-21 22:43:26 -0700 | [diff] [blame] | 1179 | trace_rcu_utilization("Start boost kthread@rcu_yield"); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1180 | spincnt = 0; |
| 1181 | } |
| 1182 | } |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1183 | /* NOTREACHED */ |
Paul E. McKenney | 385680a | 2011-06-21 22:43:26 -0700 | [diff] [blame] | 1184 | trace_rcu_utilization("End boost kthread@notreached"); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1185 | return 0; |
| 1186 | } |
| 1187 | |
| 1188 | /* |
| 1189 | * Check to see if it is time to start boosting RCU readers that are |
| 1190 | * blocking the current grace period, and, if so, tell the per-rcu_node |
| 1191 | * kthread to start boosting them. If there is an expedited grace |
| 1192 | * period in progress, it is always time to boost. |
| 1193 | * |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1194 | * The caller must hold rnp->lock, which this function releases, |
| 1195 | * but irqs remain disabled. The ->boost_kthread_task is immortal, |
| 1196 | * so we don't need to worry about it going away. |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1197 | */ |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1198 | static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1199 | { |
| 1200 | struct task_struct *t; |
| 1201 | |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1202 | if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) { |
| 1203 | rnp->n_balk_exp_gp_tasks++; |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1204 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1205 | return; |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1206 | } |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1207 | if (rnp->exp_tasks != NULL || |
| 1208 | (rnp->gp_tasks != NULL && |
| 1209 | rnp->boost_tasks == NULL && |
| 1210 | rnp->qsmask == 0 && |
| 1211 | ULONG_CMP_GE(jiffies, rnp->boost_time))) { |
| 1212 | if (rnp->exp_tasks == NULL) |
| 1213 | rnp->boost_tasks = rnp->gp_tasks; |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1214 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1215 | t = rnp->boost_kthread_task; |
| 1216 | if (t != NULL) |
| 1217 | wake_up_process(t); |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1218 | } else { |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1219 | rcu_initiate_boost_trace(rnp); |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1220 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 1221 | } |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1222 | } |
| 1223 | |
Paul E. McKenney | 0f962a5 | 2011-04-14 12:13:53 -0700 | [diff] [blame] | 1224 | /* |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1225 | * Wake up the per-CPU kthread to invoke RCU callbacks. |
| 1226 | */ |
| 1227 | static void invoke_rcu_callbacks_kthread(void) |
| 1228 | { |
| 1229 | unsigned long flags; |
| 1230 | |
| 1231 | local_irq_save(flags); |
| 1232 | __this_cpu_write(rcu_cpu_has_work, 1); |
Shaohua Li | 1eb5212 | 2011-06-16 16:02:54 -0700 | [diff] [blame] | 1233 | if (__this_cpu_read(rcu_cpu_kthread_task) != NULL && |
| 1234 | current != __this_cpu_read(rcu_cpu_kthread_task)) |
| 1235 | wake_up_process(__this_cpu_read(rcu_cpu_kthread_task)); |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1236 | local_irq_restore(flags); |
| 1237 | } |
| 1238 | |
| 1239 | /* |
Paul E. McKenney | dff1672 | 2011-11-29 15:57:13 -0800 | [diff] [blame] | 1240 | * Is the current CPU running the RCU-callbacks kthread? |
| 1241 | * Caller must have preemption disabled. |
| 1242 | */ |
| 1243 | static bool rcu_is_callbacks_kthread(void) |
| 1244 | { |
| 1245 | return __get_cpu_var(rcu_cpu_kthread_task) == current; |
| 1246 | } |
| 1247 | |
| 1248 | /* |
Paul E. McKenney | 0f962a5 | 2011-04-14 12:13:53 -0700 | [diff] [blame] | 1249 | * Set the affinity of the boost kthread. The CPU-hotplug locks are |
| 1250 | * held, so no one should be messing with the existence of the boost |
| 1251 | * kthread. |
| 1252 | */ |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1253 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, |
| 1254 | cpumask_var_t cm) |
| 1255 | { |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1256 | struct task_struct *t; |
| 1257 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1258 | t = rnp->boost_kthread_task; |
| 1259 | if (t != NULL) |
| 1260 | set_cpus_allowed_ptr(rnp->boost_kthread_task, cm); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1261 | } |
| 1262 | |
| 1263 | #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) |
| 1264 | |
| 1265 | /* |
| 1266 | * Do priority-boost accounting for the start of a new grace period. |
| 1267 | */ |
| 1268 | static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) |
| 1269 | { |
| 1270 | rnp->boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; |
| 1271 | } |
| 1272 | |
| 1273 | /* |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1274 | * Create an RCU-boost kthread for the specified node if one does not |
| 1275 | * already exist. We only create this kthread for preemptible RCU. |
| 1276 | * Returns zero if all is well, a negated errno otherwise. |
| 1277 | */ |
| 1278 | static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp, |
| 1279 | struct rcu_node *rnp, |
| 1280 | int rnp_index) |
| 1281 | { |
| 1282 | unsigned long flags; |
| 1283 | struct sched_param sp; |
| 1284 | struct task_struct *t; |
| 1285 | |
| 1286 | if (&rcu_preempt_state != rsp) |
| 1287 | return 0; |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1288 | rsp->boost = 1; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1289 | if (rnp->boost_kthread_task != NULL) |
| 1290 | return 0; |
| 1291 | t = kthread_create(rcu_boost_kthread, (void *)rnp, |
Mike Galbraith | 5b61b0b | 2011-08-19 11:39:11 -0700 | [diff] [blame] | 1292 | "rcub/%d", rnp_index); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1293 | if (IS_ERR(t)) |
| 1294 | return PTR_ERR(t); |
| 1295 | raw_spin_lock_irqsave(&rnp->lock, flags); |
| 1296 | rnp->boost_kthread_task = t; |
| 1297 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Mike Galbraith | 5b61b0b | 2011-08-19 11:39:11 -0700 | [diff] [blame] | 1298 | sp.sched_priority = RCU_BOOST_PRIO; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1299 | sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); |
Paul E. McKenney | 9a43273 | 2011-05-30 20:38:55 -0700 | [diff] [blame] | 1300 | wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1301 | return 0; |
| 1302 | } |
| 1303 | |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1304 | #ifdef CONFIG_HOTPLUG_CPU |
| 1305 | |
| 1306 | /* |
| 1307 | * Stop the RCU's per-CPU kthread when its CPU goes offline,. |
| 1308 | */ |
| 1309 | static void rcu_stop_cpu_kthread(int cpu) |
| 1310 | { |
| 1311 | struct task_struct *t; |
| 1312 | |
| 1313 | /* Stop the CPU's kthread. */ |
| 1314 | t = per_cpu(rcu_cpu_kthread_task, cpu); |
| 1315 | if (t != NULL) { |
| 1316 | per_cpu(rcu_cpu_kthread_task, cpu) = NULL; |
| 1317 | kthread_stop(t); |
| 1318 | } |
| 1319 | } |
| 1320 | |
| 1321 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
| 1322 | |
| 1323 | static void rcu_kthread_do_work(void) |
| 1324 | { |
| 1325 | rcu_do_batch(&rcu_sched_state, &__get_cpu_var(rcu_sched_data)); |
| 1326 | rcu_do_batch(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); |
| 1327 | rcu_preempt_do_callbacks(); |
| 1328 | } |
| 1329 | |
| 1330 | /* |
| 1331 | * Wake up the specified per-rcu_node-structure kthread. |
| 1332 | * Because the per-rcu_node kthreads are immortal, we don't need |
| 1333 | * to do anything to keep them alive. |
| 1334 | */ |
| 1335 | static void invoke_rcu_node_kthread(struct rcu_node *rnp) |
| 1336 | { |
| 1337 | struct task_struct *t; |
| 1338 | |
| 1339 | t = rnp->node_kthread_task; |
| 1340 | if (t != NULL) |
| 1341 | wake_up_process(t); |
| 1342 | } |
| 1343 | |
| 1344 | /* |
| 1345 | * Set the specified CPU's kthread to run RT or not, as specified by |
| 1346 | * the to_rt argument. The CPU-hotplug locks are held, so the task |
| 1347 | * is not going away. |
| 1348 | */ |
| 1349 | static void rcu_cpu_kthread_setrt(int cpu, int to_rt) |
| 1350 | { |
| 1351 | int policy; |
| 1352 | struct sched_param sp; |
| 1353 | struct task_struct *t; |
| 1354 | |
| 1355 | t = per_cpu(rcu_cpu_kthread_task, cpu); |
| 1356 | if (t == NULL) |
| 1357 | return; |
| 1358 | if (to_rt) { |
| 1359 | policy = SCHED_FIFO; |
| 1360 | sp.sched_priority = RCU_KTHREAD_PRIO; |
| 1361 | } else { |
| 1362 | policy = SCHED_NORMAL; |
| 1363 | sp.sched_priority = 0; |
| 1364 | } |
| 1365 | sched_setscheduler_nocheck(t, policy, &sp); |
| 1366 | } |
| 1367 | |
| 1368 | /* |
| 1369 | * Timer handler to initiate the waking up of per-CPU kthreads that |
| 1370 | * have yielded the CPU due to excess numbers of RCU callbacks. |
| 1371 | * We wake up the per-rcu_node kthread, which in turn will wake up |
| 1372 | * the booster kthread. |
| 1373 | */ |
| 1374 | static void rcu_cpu_kthread_timer(unsigned long arg) |
| 1375 | { |
| 1376 | struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg); |
| 1377 | struct rcu_node *rnp = rdp->mynode; |
| 1378 | |
| 1379 | atomic_or(rdp->grpmask, &rnp->wakemask); |
| 1380 | invoke_rcu_node_kthread(rnp); |
| 1381 | } |
| 1382 | |
| 1383 | /* |
| 1384 | * Drop to non-real-time priority and yield, but only after posting a |
| 1385 | * timer that will cause us to regain our real-time priority if we |
| 1386 | * remain preempted. Either way, we restore our real-time priority |
| 1387 | * before returning. |
| 1388 | */ |
| 1389 | static void rcu_yield(void (*f)(unsigned long), unsigned long arg) |
| 1390 | { |
| 1391 | struct sched_param sp; |
| 1392 | struct timer_list yield_timer; |
Mike Galbraith | 5b61b0b | 2011-08-19 11:39:11 -0700 | [diff] [blame] | 1393 | int prio = current->rt_priority; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1394 | |
| 1395 | setup_timer_on_stack(&yield_timer, f, arg); |
| 1396 | mod_timer(&yield_timer, jiffies + 2); |
| 1397 | sp.sched_priority = 0; |
| 1398 | sched_setscheduler_nocheck(current, SCHED_NORMAL, &sp); |
| 1399 | set_user_nice(current, 19); |
| 1400 | schedule(); |
Mike Galbraith | 5b61b0b | 2011-08-19 11:39:11 -0700 | [diff] [blame] | 1401 | set_user_nice(current, 0); |
| 1402 | sp.sched_priority = prio; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1403 | sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); |
| 1404 | del_timer(&yield_timer); |
| 1405 | } |
| 1406 | |
| 1407 | /* |
| 1408 | * Handle cases where the rcu_cpu_kthread() ends up on the wrong CPU. |
| 1409 | * This can happen while the corresponding CPU is either coming online |
| 1410 | * or going offline. We cannot wait until the CPU is fully online |
| 1411 | * before starting the kthread, because the various notifier functions |
| 1412 | * can wait for RCU grace periods. So we park rcu_cpu_kthread() until |
| 1413 | * the corresponding CPU is online. |
| 1414 | * |
| 1415 | * Return 1 if the kthread needs to stop, 0 otherwise. |
| 1416 | * |
| 1417 | * Caller must disable bh. This function can momentarily enable it. |
| 1418 | */ |
| 1419 | static int rcu_cpu_kthread_should_stop(int cpu) |
| 1420 | { |
| 1421 | while (cpu_is_offline(cpu) || |
| 1422 | !cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu)) || |
| 1423 | smp_processor_id() != cpu) { |
| 1424 | if (kthread_should_stop()) |
| 1425 | return 1; |
| 1426 | per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; |
| 1427 | per_cpu(rcu_cpu_kthread_cpu, cpu) = raw_smp_processor_id(); |
| 1428 | local_bh_enable(); |
| 1429 | schedule_timeout_uninterruptible(1); |
| 1430 | if (!cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu))) |
| 1431 | set_cpus_allowed_ptr(current, cpumask_of(cpu)); |
| 1432 | local_bh_disable(); |
| 1433 | } |
| 1434 | per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu; |
| 1435 | return 0; |
| 1436 | } |
| 1437 | |
| 1438 | /* |
| 1439 | * Per-CPU kernel thread that invokes RCU callbacks. This replaces the |
Paul E. McKenney | e0f2306 | 2011-06-21 01:29:39 -0700 | [diff] [blame] | 1440 | * RCU softirq used in flavors and configurations of RCU that do not |
| 1441 | * support RCU priority boosting. |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1442 | */ |
| 1443 | static int rcu_cpu_kthread(void *arg) |
| 1444 | { |
| 1445 | int cpu = (int)(long)arg; |
| 1446 | unsigned long flags; |
| 1447 | int spincnt = 0; |
| 1448 | unsigned int *statusp = &per_cpu(rcu_cpu_kthread_status, cpu); |
| 1449 | char work; |
| 1450 | char *workp = &per_cpu(rcu_cpu_has_work, cpu); |
| 1451 | |
Paul E. McKenney | 385680a | 2011-06-21 22:43:26 -0700 | [diff] [blame] | 1452 | trace_rcu_utilization("Start CPU kthread@init"); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1453 | for (;;) { |
| 1454 | *statusp = RCU_KTHREAD_WAITING; |
Paul E. McKenney | 385680a | 2011-06-21 22:43:26 -0700 | [diff] [blame] | 1455 | trace_rcu_utilization("End CPU kthread@rcu_wait"); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1456 | rcu_wait(*workp != 0 || kthread_should_stop()); |
Paul E. McKenney | 385680a | 2011-06-21 22:43:26 -0700 | [diff] [blame] | 1457 | trace_rcu_utilization("Start CPU kthread@rcu_wait"); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1458 | local_bh_disable(); |
| 1459 | if (rcu_cpu_kthread_should_stop(cpu)) { |
| 1460 | local_bh_enable(); |
| 1461 | break; |
| 1462 | } |
| 1463 | *statusp = RCU_KTHREAD_RUNNING; |
| 1464 | per_cpu(rcu_cpu_kthread_loops, cpu)++; |
| 1465 | local_irq_save(flags); |
| 1466 | work = *workp; |
| 1467 | *workp = 0; |
| 1468 | local_irq_restore(flags); |
| 1469 | if (work) |
| 1470 | rcu_kthread_do_work(); |
| 1471 | local_bh_enable(); |
| 1472 | if (*workp != 0) |
| 1473 | spincnt++; |
| 1474 | else |
| 1475 | spincnt = 0; |
| 1476 | if (spincnt > 10) { |
| 1477 | *statusp = RCU_KTHREAD_YIELDING; |
Paul E. McKenney | 385680a | 2011-06-21 22:43:26 -0700 | [diff] [blame] | 1478 | trace_rcu_utilization("End CPU kthread@rcu_yield"); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1479 | rcu_yield(rcu_cpu_kthread_timer, (unsigned long)cpu); |
Paul E. McKenney | 385680a | 2011-06-21 22:43:26 -0700 | [diff] [blame] | 1480 | trace_rcu_utilization("Start CPU kthread@rcu_yield"); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1481 | spincnt = 0; |
| 1482 | } |
| 1483 | } |
| 1484 | *statusp = RCU_KTHREAD_STOPPED; |
Paul E. McKenney | 385680a | 2011-06-21 22:43:26 -0700 | [diff] [blame] | 1485 | trace_rcu_utilization("End CPU kthread@term"); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1486 | return 0; |
| 1487 | } |
| 1488 | |
| 1489 | /* |
| 1490 | * Spawn a per-CPU kthread, setting up affinity and priority. |
| 1491 | * Because the CPU hotplug lock is held, no other CPU will be attempting |
| 1492 | * to manipulate rcu_cpu_kthread_task. There might be another CPU |
| 1493 | * attempting to access it during boot, but the locking in kthread_bind() |
| 1494 | * will enforce sufficient ordering. |
| 1495 | * |
| 1496 | * Please note that we cannot simply refuse to wake up the per-CPU |
| 1497 | * kthread because kthreads are created in TASK_UNINTERRUPTIBLE state, |
| 1498 | * which can result in softlockup complaints if the task ends up being |
| 1499 | * idle for more than a couple of minutes. |
| 1500 | * |
| 1501 | * However, please note also that we cannot bind the per-CPU kthread to its |
| 1502 | * CPU until that CPU is fully online. We also cannot wait until the |
| 1503 | * CPU is fully online before we create its per-CPU kthread, as this would |
| 1504 | * deadlock the system when CPU notifiers tried waiting for grace |
| 1505 | * periods. So we bind the per-CPU kthread to its CPU only if the CPU |
| 1506 | * is online. If its CPU is not yet fully online, then the code in |
| 1507 | * rcu_cpu_kthread() will wait until it is fully online, and then do |
| 1508 | * the binding. |
| 1509 | */ |
| 1510 | static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu) |
| 1511 | { |
| 1512 | struct sched_param sp; |
| 1513 | struct task_struct *t; |
| 1514 | |
Paul E. McKenney | b0d3041 | 2011-07-10 15:57:35 -0700 | [diff] [blame] | 1515 | if (!rcu_scheduler_fully_active || |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1516 | per_cpu(rcu_cpu_kthread_task, cpu) != NULL) |
| 1517 | return 0; |
Eric Dumazet | 1f28809 | 2011-06-16 15:53:18 -0700 | [diff] [blame] | 1518 | t = kthread_create_on_node(rcu_cpu_kthread, |
| 1519 | (void *)(long)cpu, |
| 1520 | cpu_to_node(cpu), |
Mike Galbraith | 5b61b0b | 2011-08-19 11:39:11 -0700 | [diff] [blame] | 1521 | "rcuc/%d", cpu); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1522 | if (IS_ERR(t)) |
| 1523 | return PTR_ERR(t); |
| 1524 | if (cpu_online(cpu)) |
| 1525 | kthread_bind(t, cpu); |
| 1526 | per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu; |
| 1527 | WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL); |
| 1528 | sp.sched_priority = RCU_KTHREAD_PRIO; |
| 1529 | sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); |
| 1530 | per_cpu(rcu_cpu_kthread_task, cpu) = t; |
| 1531 | wake_up_process(t); /* Get to TASK_INTERRUPTIBLE quickly. */ |
| 1532 | return 0; |
| 1533 | } |
| 1534 | |
| 1535 | /* |
| 1536 | * Per-rcu_node kthread, which is in charge of waking up the per-CPU |
| 1537 | * kthreads when needed. We ignore requests to wake up kthreads |
| 1538 | * for offline CPUs, which is OK because force_quiescent_state() |
| 1539 | * takes care of this case. |
| 1540 | */ |
| 1541 | static int rcu_node_kthread(void *arg) |
| 1542 | { |
| 1543 | int cpu; |
| 1544 | unsigned long flags; |
| 1545 | unsigned long mask; |
| 1546 | struct rcu_node *rnp = (struct rcu_node *)arg; |
| 1547 | struct sched_param sp; |
| 1548 | struct task_struct *t; |
| 1549 | |
| 1550 | for (;;) { |
| 1551 | rnp->node_kthread_status = RCU_KTHREAD_WAITING; |
| 1552 | rcu_wait(atomic_read(&rnp->wakemask) != 0); |
| 1553 | rnp->node_kthread_status = RCU_KTHREAD_RUNNING; |
| 1554 | raw_spin_lock_irqsave(&rnp->lock, flags); |
| 1555 | mask = atomic_xchg(&rnp->wakemask, 0); |
| 1556 | rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */ |
| 1557 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) { |
| 1558 | if ((mask & 0x1) == 0) |
| 1559 | continue; |
| 1560 | preempt_disable(); |
| 1561 | t = per_cpu(rcu_cpu_kthread_task, cpu); |
| 1562 | if (!cpu_online(cpu) || t == NULL) { |
| 1563 | preempt_enable(); |
| 1564 | continue; |
| 1565 | } |
| 1566 | per_cpu(rcu_cpu_has_work, cpu) = 1; |
| 1567 | sp.sched_priority = RCU_KTHREAD_PRIO; |
| 1568 | sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); |
| 1569 | preempt_enable(); |
| 1570 | } |
| 1571 | } |
| 1572 | /* NOTREACHED */ |
| 1573 | rnp->node_kthread_status = RCU_KTHREAD_STOPPED; |
| 1574 | return 0; |
| 1575 | } |
| 1576 | |
| 1577 | /* |
| 1578 | * Set the per-rcu_node kthread's affinity to cover all CPUs that are |
| 1579 | * served by the rcu_node in question. The CPU hotplug lock is still |
| 1580 | * held, so the value of rnp->qsmaskinit will be stable. |
| 1581 | * |
| 1582 | * We don't include outgoingcpu in the affinity set, use -1 if there is |
| 1583 | * no outgoing CPU. If there are no CPUs left in the affinity set, |
| 1584 | * this function allows the kthread to execute on any CPU. |
| 1585 | */ |
| 1586 | static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
| 1587 | { |
| 1588 | cpumask_var_t cm; |
| 1589 | int cpu; |
| 1590 | unsigned long mask = rnp->qsmaskinit; |
| 1591 | |
| 1592 | if (rnp->node_kthread_task == NULL) |
| 1593 | return; |
| 1594 | if (!alloc_cpumask_var(&cm, GFP_KERNEL)) |
| 1595 | return; |
| 1596 | cpumask_clear(cm); |
| 1597 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) |
| 1598 | if ((mask & 0x1) && cpu != outgoingcpu) |
| 1599 | cpumask_set_cpu(cpu, cm); |
| 1600 | if (cpumask_weight(cm) == 0) { |
| 1601 | cpumask_setall(cm); |
| 1602 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) |
| 1603 | cpumask_clear_cpu(cpu, cm); |
| 1604 | WARN_ON_ONCE(cpumask_weight(cm) == 0); |
| 1605 | } |
| 1606 | set_cpus_allowed_ptr(rnp->node_kthread_task, cm); |
| 1607 | rcu_boost_kthread_setaffinity(rnp, cm); |
| 1608 | free_cpumask_var(cm); |
| 1609 | } |
| 1610 | |
| 1611 | /* |
| 1612 | * Spawn a per-rcu_node kthread, setting priority and affinity. |
| 1613 | * Called during boot before online/offline can happen, or, if |
| 1614 | * during runtime, with the main CPU-hotplug locks held. So only |
| 1615 | * one of these can be executing at a time. |
| 1616 | */ |
| 1617 | static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp, |
| 1618 | struct rcu_node *rnp) |
| 1619 | { |
| 1620 | unsigned long flags; |
| 1621 | int rnp_index = rnp - &rsp->node[0]; |
| 1622 | struct sched_param sp; |
| 1623 | struct task_struct *t; |
| 1624 | |
Paul E. McKenney | b0d3041 | 2011-07-10 15:57:35 -0700 | [diff] [blame] | 1625 | if (!rcu_scheduler_fully_active || |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1626 | rnp->qsmaskinit == 0) |
| 1627 | return 0; |
| 1628 | if (rnp->node_kthread_task == NULL) { |
| 1629 | t = kthread_create(rcu_node_kthread, (void *)rnp, |
Mike Galbraith | 5b61b0b | 2011-08-19 11:39:11 -0700 | [diff] [blame] | 1630 | "rcun/%d", rnp_index); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1631 | if (IS_ERR(t)) |
| 1632 | return PTR_ERR(t); |
| 1633 | raw_spin_lock_irqsave(&rnp->lock, flags); |
| 1634 | rnp->node_kthread_task = t; |
| 1635 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 1636 | sp.sched_priority = 99; |
| 1637 | sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); |
| 1638 | wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ |
| 1639 | } |
| 1640 | return rcu_spawn_one_boost_kthread(rsp, rnp, rnp_index); |
| 1641 | } |
| 1642 | |
| 1643 | /* |
| 1644 | * Spawn all kthreads -- called as soon as the scheduler is running. |
| 1645 | */ |
| 1646 | static int __init rcu_spawn_kthreads(void) |
| 1647 | { |
| 1648 | int cpu; |
| 1649 | struct rcu_node *rnp; |
| 1650 | |
Paul E. McKenney | b0d3041 | 2011-07-10 15:57:35 -0700 | [diff] [blame] | 1651 | rcu_scheduler_fully_active = 1; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1652 | for_each_possible_cpu(cpu) { |
| 1653 | per_cpu(rcu_cpu_has_work, cpu) = 0; |
| 1654 | if (cpu_online(cpu)) |
| 1655 | (void)rcu_spawn_one_cpu_kthread(cpu); |
| 1656 | } |
| 1657 | rnp = rcu_get_root(rcu_state); |
| 1658 | (void)rcu_spawn_one_node_kthread(rcu_state, rnp); |
| 1659 | if (NUM_RCU_NODES > 1) { |
| 1660 | rcu_for_each_leaf_node(rcu_state, rnp) |
| 1661 | (void)rcu_spawn_one_node_kthread(rcu_state, rnp); |
| 1662 | } |
| 1663 | return 0; |
| 1664 | } |
| 1665 | early_initcall(rcu_spawn_kthreads); |
| 1666 | |
| 1667 | static void __cpuinit rcu_prepare_kthreads(int cpu) |
| 1668 | { |
| 1669 | struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu); |
| 1670 | struct rcu_node *rnp = rdp->mynode; |
| 1671 | |
| 1672 | /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */ |
Paul E. McKenney | b0d3041 | 2011-07-10 15:57:35 -0700 | [diff] [blame] | 1673 | if (rcu_scheduler_fully_active) { |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1674 | (void)rcu_spawn_one_cpu_kthread(cpu); |
| 1675 | if (rnp->node_kthread_task == NULL) |
| 1676 | (void)rcu_spawn_one_node_kthread(rcu_state, rnp); |
| 1677 | } |
| 1678 | } |
| 1679 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1680 | #else /* #ifdef CONFIG_RCU_BOOST */ |
| 1681 | |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1682 | static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1683 | { |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1684 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1685 | } |
| 1686 | |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1687 | static void invoke_rcu_callbacks_kthread(void) |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1688 | { |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1689 | WARN_ON_ONCE(1); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1690 | } |
| 1691 | |
Paul E. McKenney | dff1672 | 2011-11-29 15:57:13 -0800 | [diff] [blame] | 1692 | static bool rcu_is_callbacks_kthread(void) |
| 1693 | { |
| 1694 | return false; |
| 1695 | } |
| 1696 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1697 | static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) |
| 1698 | { |
| 1699 | } |
| 1700 | |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1701 | #ifdef CONFIG_HOTPLUG_CPU |
| 1702 | |
| 1703 | static void rcu_stop_cpu_kthread(int cpu) |
| 1704 | { |
| 1705 | } |
| 1706 | |
| 1707 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
| 1708 | |
| 1709 | static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
| 1710 | { |
| 1711 | } |
| 1712 | |
| 1713 | static void rcu_cpu_kthread_setrt(int cpu, int to_rt) |
| 1714 | { |
| 1715 | } |
| 1716 | |
Paul E. McKenney | b0d3041 | 2011-07-10 15:57:35 -0700 | [diff] [blame] | 1717 | static int __init rcu_scheduler_really_started(void) |
| 1718 | { |
| 1719 | rcu_scheduler_fully_active = 1; |
| 1720 | return 0; |
| 1721 | } |
| 1722 | early_initcall(rcu_scheduler_really_started); |
| 1723 | |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1724 | static void __cpuinit rcu_prepare_kthreads(int cpu) |
| 1725 | { |
| 1726 | } |
| 1727 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1728 | #endif /* #else #ifdef CONFIG_RCU_BOOST */ |
| 1729 | |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1730 | #if !defined(CONFIG_RCU_FAST_NO_HZ) |
| 1731 | |
| 1732 | /* |
| 1733 | * Check to see if any future RCU-related work will need to be done |
| 1734 | * by the current CPU, even if none need be done immediately, returning |
| 1735 | * 1 if so. This function is part of the RCU implementation; it is -not- |
| 1736 | * an exported member of the RCU API. |
| 1737 | * |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1738 | * Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs |
| 1739 | * any flavor of RCU. |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1740 | */ |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1741 | int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies) |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1742 | { |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1743 | *delta_jiffies = ULONG_MAX; |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 1744 | return rcu_cpu_has_callbacks(cpu); |
| 1745 | } |
| 1746 | |
| 1747 | /* |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1748 | * Because we do not have RCU_FAST_NO_HZ, don't bother initializing for it. |
| 1749 | */ |
| 1750 | static void rcu_prepare_for_idle_init(int cpu) |
| 1751 | { |
| 1752 | } |
| 1753 | |
| 1754 | /* |
| 1755 | * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up |
| 1756 | * after it. |
| 1757 | */ |
| 1758 | static void rcu_cleanup_after_idle(int cpu) |
| 1759 | { |
| 1760 | } |
| 1761 | |
| 1762 | /* |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1763 | * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=n, |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 1764 | * is nothing. |
| 1765 | */ |
| 1766 | static void rcu_prepare_for_idle(int cpu) |
| 1767 | { |
| 1768 | } |
| 1769 | |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 1770 | /* |
| 1771 | * Don't bother keeping a running count of the number of RCU callbacks |
| 1772 | * posted because CONFIG_RCU_FAST_NO_HZ=n. |
| 1773 | */ |
| 1774 | static void rcu_idle_count_callbacks_posted(void) |
| 1775 | { |
| 1776 | } |
| 1777 | |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1778 | #else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |
| 1779 | |
Paul E. McKenney | f23f7fa | 2011-11-30 15:41:14 -0800 | [diff] [blame] | 1780 | /* |
| 1781 | * This code is invoked when a CPU goes idle, at which point we want |
| 1782 | * to have the CPU do everything required for RCU so that it can enter |
| 1783 | * the energy-efficient dyntick-idle mode. This is handled by a |
| 1784 | * state machine implemented by rcu_prepare_for_idle() below. |
| 1785 | * |
| 1786 | * The following three proprocessor symbols control this state machine: |
| 1787 | * |
| 1788 | * RCU_IDLE_FLUSHES gives the maximum number of times that we will attempt |
| 1789 | * to satisfy RCU. Beyond this point, it is better to incur a periodic |
| 1790 | * scheduling-clock interrupt than to loop through the state machine |
| 1791 | * at full power. |
| 1792 | * RCU_IDLE_OPT_FLUSHES gives the number of RCU_IDLE_FLUSHES that are |
| 1793 | * optional if RCU does not need anything immediately from this |
| 1794 | * CPU, even if this CPU still has RCU callbacks queued. The first |
| 1795 | * times through the state machine are mandatory: we need to give |
| 1796 | * the state machine a chance to communicate a quiescent state |
| 1797 | * to the RCU core. |
| 1798 | * RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted |
| 1799 | * to sleep in dyntick-idle mode with RCU callbacks pending. This |
| 1800 | * is sized to be roughly one RCU grace period. Those energy-efficiency |
| 1801 | * benchmarkers who might otherwise be tempted to set this to a large |
| 1802 | * number, be warned: Setting RCU_IDLE_GP_DELAY too high can hang your |
| 1803 | * system. And if you are -that- concerned about energy efficiency, |
| 1804 | * just power the system down and be done with it! |
Paul E. McKenney | 778d250 | 2012-01-10 14:13:24 -0800 | [diff] [blame] | 1805 | * RCU_IDLE_LAZY_GP_DELAY gives the number of jiffies that a CPU is |
| 1806 | * permitted to sleep in dyntick-idle mode with only lazy RCU |
| 1807 | * callbacks pending. Setting this too high can OOM your system. |
Paul E. McKenney | f23f7fa | 2011-11-30 15:41:14 -0800 | [diff] [blame] | 1808 | * |
| 1809 | * The values below work well in practice. If future workloads require |
| 1810 | * adjustment, they can be converted into kernel config parameters, though |
| 1811 | * making the state machine smarter might be a better option. |
| 1812 | */ |
| 1813 | #define RCU_IDLE_FLUSHES 5 /* Number of dyntick-idle tries. */ |
| 1814 | #define RCU_IDLE_OPT_FLUSHES 3 /* Optional dyntick-idle tries. */ |
Paul E. McKenney | e84c48a | 2012-06-04 20:45:10 -0700 | [diff] [blame] | 1815 | #define RCU_IDLE_GP_DELAY 4 /* Roughly one grace period. */ |
Paul E. McKenney | 778d250 | 2012-01-10 14:13:24 -0800 | [diff] [blame] | 1816 | #define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */ |
Paul E. McKenney | f23f7fa | 2011-11-30 15:41:14 -0800 | [diff] [blame] | 1817 | |
Paul E. McKenney | 9d2ad24 | 2012-06-24 10:15:02 -0700 | [diff] [blame] | 1818 | extern int tick_nohz_enabled; |
| 1819 | |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1820 | /* |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 1821 | * Does the specified flavor of RCU have non-lazy callbacks pending on |
| 1822 | * the specified CPU? Both RCU flavor and CPU are specified by the |
| 1823 | * rcu_data structure. |
| 1824 | */ |
| 1825 | static bool __rcu_cpu_has_nonlazy_callbacks(struct rcu_data *rdp) |
| 1826 | { |
| 1827 | return rdp->qlen != rdp->qlen_lazy; |
| 1828 | } |
| 1829 | |
| 1830 | #ifdef CONFIG_TREE_PREEMPT_RCU |
| 1831 | |
| 1832 | /* |
| 1833 | * Are there non-lazy RCU-preempt callbacks? (There cannot be if there |
| 1834 | * is no RCU-preempt in the kernel.) |
| 1835 | */ |
| 1836 | static bool rcu_preempt_cpu_has_nonlazy_callbacks(int cpu) |
| 1837 | { |
| 1838 | struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu); |
| 1839 | |
| 1840 | return __rcu_cpu_has_nonlazy_callbacks(rdp); |
| 1841 | } |
| 1842 | |
| 1843 | #else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ |
| 1844 | |
| 1845 | static bool rcu_preempt_cpu_has_nonlazy_callbacks(int cpu) |
| 1846 | { |
| 1847 | return 0; |
| 1848 | } |
| 1849 | |
| 1850 | #endif /* else #ifdef CONFIG_TREE_PREEMPT_RCU */ |
| 1851 | |
| 1852 | /* |
| 1853 | * Does any flavor of RCU have non-lazy callbacks on the specified CPU? |
| 1854 | */ |
| 1855 | static bool rcu_cpu_has_nonlazy_callbacks(int cpu) |
| 1856 | { |
| 1857 | return __rcu_cpu_has_nonlazy_callbacks(&per_cpu(rcu_sched_data, cpu)) || |
| 1858 | __rcu_cpu_has_nonlazy_callbacks(&per_cpu(rcu_bh_data, cpu)) || |
| 1859 | rcu_preempt_cpu_has_nonlazy_callbacks(cpu); |
| 1860 | } |
| 1861 | |
| 1862 | /* |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1863 | * Allow the CPU to enter dyntick-idle mode if either: (1) There are no |
| 1864 | * callbacks on this CPU, (2) this CPU has not yet attempted to enter |
| 1865 | * dyntick-idle mode, or (3) this CPU is in the process of attempting to |
| 1866 | * enter dyntick-idle mode. Otherwise, if we have recently tried and failed |
| 1867 | * to enter dyntick-idle mode, we refuse to try to enter it. After all, |
| 1868 | * it is better to incur scheduling-clock interrupts than to spin |
| 1869 | * continuously for the same time duration! |
| 1870 | * |
| 1871 | * The delta_jiffies argument is used to store the time when RCU is |
| 1872 | * going to need the CPU again if it still has callbacks. The reason |
| 1873 | * for this is that rcu_prepare_for_idle() might need to post a timer, |
| 1874 | * but if so, it will do so after tick_nohz_stop_sched_tick() has set |
| 1875 | * the wakeup time for this CPU. This means that RCU's timer can be |
| 1876 | * delayed until the wakeup time, which defeats the purpose of posting |
| 1877 | * a timer. |
| 1878 | */ |
| 1879 | int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies) |
| 1880 | { |
| 1881 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); |
| 1882 | |
| 1883 | /* Flag a new idle sojourn to the idle-entry state machine. */ |
| 1884 | rdtp->idle_first_pass = 1; |
| 1885 | /* If no callbacks, RCU doesn't need the CPU. */ |
| 1886 | if (!rcu_cpu_has_callbacks(cpu)) { |
| 1887 | *delta_jiffies = ULONG_MAX; |
| 1888 | return 0; |
| 1889 | } |
| 1890 | if (rdtp->dyntick_holdoff == jiffies) { |
| 1891 | /* RCU recently tried and failed, so don't try again. */ |
| 1892 | *delta_jiffies = 1; |
| 1893 | return 1; |
| 1894 | } |
| 1895 | /* Set up for the possibility that RCU will post a timer. */ |
Paul E. McKenney | e84c48a | 2012-06-04 20:45:10 -0700 | [diff] [blame] | 1896 | if (rcu_cpu_has_nonlazy_callbacks(cpu)) { |
| 1897 | *delta_jiffies = round_up(RCU_IDLE_GP_DELAY + jiffies, |
| 1898 | RCU_IDLE_GP_DELAY) - jiffies; |
| 1899 | } else { |
| 1900 | *delta_jiffies = jiffies + RCU_IDLE_LAZY_GP_DELAY; |
| 1901 | *delta_jiffies = round_jiffies(*delta_jiffies) - jiffies; |
| 1902 | } |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1903 | return 0; |
| 1904 | } |
| 1905 | |
| 1906 | /* |
Paul E. McKenney | 21e52e1 | 2012-04-30 14:16:19 -0700 | [diff] [blame] | 1907 | * Handler for smp_call_function_single(). The only point of this |
| 1908 | * handler is to wake the CPU up, so the handler does only tracing. |
| 1909 | */ |
| 1910 | void rcu_idle_demigrate(void *unused) |
| 1911 | { |
| 1912 | trace_rcu_prep_idle("Demigrate"); |
| 1913 | } |
| 1914 | |
| 1915 | /* |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1916 | * Timer handler used to force CPU to start pushing its remaining RCU |
| 1917 | * callbacks in the case where it entered dyntick-idle mode with callbacks |
| 1918 | * pending. The hander doesn't really need to do anything because the |
| 1919 | * real work is done upon re-entry to idle, or by the next scheduling-clock |
| 1920 | * interrupt should idle not be re-entered. |
Paul E. McKenney | 21e52e1 | 2012-04-30 14:16:19 -0700 | [diff] [blame] | 1921 | * |
| 1922 | * One special case: the timer gets migrated without awakening the CPU |
| 1923 | * on which the timer was scheduled on. In this case, we must wake up |
| 1924 | * that CPU. We do so with smp_call_function_single(). |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1925 | */ |
Paul E. McKenney | 21e52e1 | 2012-04-30 14:16:19 -0700 | [diff] [blame] | 1926 | static void rcu_idle_gp_timer_func(unsigned long cpu_in) |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1927 | { |
Paul E. McKenney | 21e52e1 | 2012-04-30 14:16:19 -0700 | [diff] [blame] | 1928 | int cpu = (int)cpu_in; |
| 1929 | |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1930 | trace_rcu_prep_idle("Timer"); |
Paul E. McKenney | 21e52e1 | 2012-04-30 14:16:19 -0700 | [diff] [blame] | 1931 | if (cpu != smp_processor_id()) |
| 1932 | smp_call_function_single(cpu, rcu_idle_demigrate, NULL, 0); |
| 1933 | else |
| 1934 | WARN_ON_ONCE(1); /* Getting here can hang the system... */ |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1935 | } |
| 1936 | |
| 1937 | /* |
| 1938 | * Initialize the timer used to pull CPUs out of dyntick-idle mode. |
| 1939 | */ |
| 1940 | static void rcu_prepare_for_idle_init(int cpu) |
| 1941 | { |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 1942 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); |
| 1943 | |
| 1944 | rdtp->dyntick_holdoff = jiffies - 1; |
| 1945 | setup_timer(&rdtp->idle_gp_timer, rcu_idle_gp_timer_func, cpu); |
| 1946 | rdtp->idle_gp_timer_expires = jiffies - 1; |
| 1947 | rdtp->idle_first_pass = 1; |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1948 | } |
| 1949 | |
| 1950 | /* |
| 1951 | * Clean up for exit from idle. Because we are exiting from idle, there |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 1952 | * is no longer any point to ->idle_gp_timer, so cancel it. This will |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1953 | * do nothing if this timer is not active, so just cancel it unconditionally. |
| 1954 | */ |
| 1955 | static void rcu_cleanup_after_idle(int cpu) |
| 1956 | { |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 1957 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); |
| 1958 | |
| 1959 | del_timer(&rdtp->idle_gp_timer); |
Paul E. McKenney | 2fdbb31 | 2012-02-23 15:58:29 -0800 | [diff] [blame] | 1960 | trace_rcu_prep_idle("Cleanup after idle"); |
Paul E. McKenney | 9d2ad24 | 2012-06-24 10:15:02 -0700 | [diff] [blame] | 1961 | rdtp->tick_nohz_enabled_snap = ACCESS_ONCE(tick_nohz_enabled); |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1962 | } |
| 1963 | |
| 1964 | /* |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 1965 | * Check to see if any RCU-related work can be done by the current CPU, |
| 1966 | * and if so, schedule a softirq to get it done. This function is part |
| 1967 | * of the RCU implementation; it is -not- an exported member of the RCU API. |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1968 | * |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 1969 | * The idea is for the current CPU to clear out all work required by the |
| 1970 | * RCU core for the current grace period, so that this CPU can be permitted |
| 1971 | * to enter dyntick-idle mode. In some cases, it will need to be awakened |
| 1972 | * at the end of the grace period by whatever CPU ends the grace period. |
| 1973 | * This allows CPUs to go dyntick-idle more quickly, and to reduce the |
| 1974 | * number of wakeups by a modest integer factor. |
Paul E. McKenney | a47cd88 | 2010-02-26 16:38:56 -0800 | [diff] [blame] | 1975 | * |
| 1976 | * Because it is not legal to invoke rcu_process_callbacks() with irqs |
| 1977 | * disabled, we do one pass of force_quiescent_state(), then do a |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1978 | * invoke_rcu_core() to cause rcu_process_callbacks() to be invoked |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 1979 | * later. The ->dyntick_drain field controls the sequencing. |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 1980 | * |
| 1981 | * The caller must have disabled interrupts. |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1982 | */ |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 1983 | static void rcu_prepare_for_idle(int cpu) |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1984 | { |
Paul E. McKenney | f511fc6 | 2012-03-15 12:16:26 -0700 | [diff] [blame] | 1985 | struct timer_list *tp; |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 1986 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); |
Paul E. McKenney | 9d2ad24 | 2012-06-24 10:15:02 -0700 | [diff] [blame] | 1987 | int tne; |
| 1988 | |
| 1989 | /* Handle nohz enablement switches conservatively. */ |
| 1990 | tne = ACCESS_ONCE(tick_nohz_enabled); |
| 1991 | if (tne != rdtp->tick_nohz_enabled_snap) { |
| 1992 | if (rcu_cpu_has_callbacks(cpu)) |
| 1993 | invoke_rcu_core(); /* force nohz to see update. */ |
| 1994 | rdtp->tick_nohz_enabled_snap = tne; |
| 1995 | return; |
| 1996 | } |
| 1997 | if (!tne) |
| 1998 | return; |
Paul E. McKenney | f511fc6 | 2012-03-15 12:16:26 -0700 | [diff] [blame] | 1999 | |
Paul E. McKenney | 3084f2f | 2011-11-22 17:07:11 -0800 | [diff] [blame] | 2000 | /* |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 2001 | * If this is an idle re-entry, for example, due to use of |
| 2002 | * RCU_NONIDLE() or the new idle-loop tracing API within the idle |
| 2003 | * loop, then don't take any state-machine actions, unless the |
| 2004 | * momentary exit from idle queued additional non-lazy callbacks. |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2005 | * Instead, repost the ->idle_gp_timer if this CPU has callbacks |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 2006 | * pending. |
| 2007 | */ |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2008 | if (!rdtp->idle_first_pass && |
| 2009 | (rdtp->nonlazy_posted == rdtp->nonlazy_posted_snap)) { |
Paul E. McKenney | f511fc6 | 2012-03-15 12:16:26 -0700 | [diff] [blame] | 2010 | if (rcu_cpu_has_callbacks(cpu)) { |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2011 | tp = &rdtp->idle_gp_timer; |
| 2012 | mod_timer_pinned(tp, rdtp->idle_gp_timer_expires); |
Paul E. McKenney | f511fc6 | 2012-03-15 12:16:26 -0700 | [diff] [blame] | 2013 | } |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 2014 | return; |
| 2015 | } |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2016 | rdtp->idle_first_pass = 0; |
| 2017 | rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted - 1; |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 2018 | |
| 2019 | /* |
Paul E. McKenney | f535a60 | 2011-11-22 20:43:02 -0800 | [diff] [blame] | 2020 | * If there are no callbacks on this CPU, enter dyntick-idle mode. |
| 2021 | * Also reset state to avoid prejudicing later attempts. |
Paul E. McKenney | 3084f2f | 2011-11-22 17:07:11 -0800 | [diff] [blame] | 2022 | */ |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 2023 | if (!rcu_cpu_has_callbacks(cpu)) { |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2024 | rdtp->dyntick_holdoff = jiffies - 1; |
| 2025 | rdtp->dyntick_drain = 0; |
Paul E. McKenney | 433cddd | 2011-11-22 14:58:03 -0800 | [diff] [blame] | 2026 | trace_rcu_prep_idle("No callbacks"); |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 2027 | return; |
Paul E. McKenney | 77e38ed | 2010-04-25 21:04:29 -0700 | [diff] [blame] | 2028 | } |
Paul E. McKenney | 3084f2f | 2011-11-22 17:07:11 -0800 | [diff] [blame] | 2029 | |
| 2030 | /* |
| 2031 | * If in holdoff mode, just return. We will presumably have |
| 2032 | * refrained from disabling the scheduling-clock tick. |
| 2033 | */ |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2034 | if (rdtp->dyntick_holdoff == jiffies) { |
Paul E. McKenney | 433cddd | 2011-11-22 14:58:03 -0800 | [diff] [blame] | 2035 | trace_rcu_prep_idle("In holdoff"); |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 2036 | return; |
Paul E. McKenney | 433cddd | 2011-11-22 14:58:03 -0800 | [diff] [blame] | 2037 | } |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 2038 | |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2039 | /* Check and update the ->dyntick_drain sequencing. */ |
| 2040 | if (rdtp->dyntick_drain <= 0) { |
Paul E. McKenney | a47cd88 | 2010-02-26 16:38:56 -0800 | [diff] [blame] | 2041 | /* First time through, initialize the counter. */ |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2042 | rdtp->dyntick_drain = RCU_IDLE_FLUSHES; |
| 2043 | } else if (rdtp->dyntick_drain <= RCU_IDLE_OPT_FLUSHES && |
Paul E. McKenney | c3ce910 | 2012-02-14 10:12:54 -0800 | [diff] [blame] | 2044 | !rcu_pending(cpu) && |
| 2045 | !local_softirq_pending()) { |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 2046 | /* Can we go dyntick-idle despite still having callbacks? */ |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2047 | rdtp->dyntick_drain = 0; |
| 2048 | rdtp->dyntick_holdoff = jiffies; |
Paul E. McKenney | fd4b352 | 2012-05-05 19:10:35 -0700 | [diff] [blame] | 2049 | if (rcu_cpu_has_nonlazy_callbacks(cpu)) { |
| 2050 | trace_rcu_prep_idle("Dyntick with callbacks"); |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2051 | rdtp->idle_gp_timer_expires = |
Paul E. McKenney | e84c48a | 2012-06-04 20:45:10 -0700 | [diff] [blame] | 2052 | round_up(jiffies + RCU_IDLE_GP_DELAY, |
| 2053 | RCU_IDLE_GP_DELAY); |
Paul E. McKenney | fd4b352 | 2012-05-05 19:10:35 -0700 | [diff] [blame] | 2054 | } else { |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2055 | rdtp->idle_gp_timer_expires = |
Paul E. McKenney | e84c48a | 2012-06-04 20:45:10 -0700 | [diff] [blame] | 2056 | round_jiffies(jiffies + RCU_IDLE_LAZY_GP_DELAY); |
Paul E. McKenney | fd4b352 | 2012-05-05 19:10:35 -0700 | [diff] [blame] | 2057 | trace_rcu_prep_idle("Dyntick with lazy callbacks"); |
| 2058 | } |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2059 | tp = &rdtp->idle_gp_timer; |
| 2060 | mod_timer_pinned(tp, rdtp->idle_gp_timer_expires); |
| 2061 | rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; |
Paul E. McKenney | f23f7fa | 2011-11-30 15:41:14 -0800 | [diff] [blame] | 2062 | return; /* Nothing more to do immediately. */ |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2063 | } else if (--(rdtp->dyntick_drain) <= 0) { |
Paul E. McKenney | a47cd88 | 2010-02-26 16:38:56 -0800 | [diff] [blame] | 2064 | /* We have hit the limit, so time to give up. */ |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2065 | rdtp->dyntick_holdoff = jiffies; |
Paul E. McKenney | 433cddd | 2011-11-22 14:58:03 -0800 | [diff] [blame] | 2066 | trace_rcu_prep_idle("Begin holdoff"); |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 2067 | invoke_rcu_core(); /* Force the CPU out of dyntick-idle. */ |
| 2068 | return; |
Paul E. McKenney | a47cd88 | 2010-02-26 16:38:56 -0800 | [diff] [blame] | 2069 | } |
| 2070 | |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 2071 | /* |
| 2072 | * Do one step of pushing the remaining RCU callbacks through |
| 2073 | * the RCU core state machine. |
| 2074 | */ |
| 2075 | #ifdef CONFIG_TREE_PREEMPT_RCU |
| 2076 | if (per_cpu(rcu_preempt_data, cpu).nxtlist) { |
| 2077 | rcu_preempt_qs(cpu); |
| 2078 | force_quiescent_state(&rcu_preempt_state, 0); |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 2079 | } |
| 2080 | #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ |
Paul E. McKenney | a47cd88 | 2010-02-26 16:38:56 -0800 | [diff] [blame] | 2081 | if (per_cpu(rcu_sched_data, cpu).nxtlist) { |
| 2082 | rcu_sched_qs(cpu); |
| 2083 | force_quiescent_state(&rcu_sched_state, 0); |
Paul E. McKenney | a47cd88 | 2010-02-26 16:38:56 -0800 | [diff] [blame] | 2084 | } |
| 2085 | if (per_cpu(rcu_bh_data, cpu).nxtlist) { |
| 2086 | rcu_bh_qs(cpu); |
| 2087 | force_quiescent_state(&rcu_bh_state, 0); |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 2088 | } |
| 2089 | |
Paul E. McKenney | 433cddd | 2011-11-22 14:58:03 -0800 | [diff] [blame] | 2090 | /* |
| 2091 | * If RCU callbacks are still pending, RCU still needs this CPU. |
| 2092 | * So try forcing the callbacks through the grace period. |
| 2093 | */ |
Paul E. McKenney | 3ad0dec | 2011-11-22 21:08:13 -0800 | [diff] [blame] | 2094 | if (rcu_cpu_has_callbacks(cpu)) { |
Paul E. McKenney | 433cddd | 2011-11-22 14:58:03 -0800 | [diff] [blame] | 2095 | trace_rcu_prep_idle("More callbacks"); |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 2096 | invoke_rcu_core(); |
Paul E. McKenney | c701d5d | 2012-06-28 08:08:25 -0700 | [diff] [blame] | 2097 | } else { |
Paul E. McKenney | 433cddd | 2011-11-22 14:58:03 -0800 | [diff] [blame] | 2098 | trace_rcu_prep_idle("Callbacks drained"); |
Paul E. McKenney | c701d5d | 2012-06-28 08:08:25 -0700 | [diff] [blame] | 2099 | } |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 2100 | } |
| 2101 | |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 2102 | /* |
Paul E. McKenney | 98248a0 | 2012-05-03 15:38:10 -0700 | [diff] [blame] | 2103 | * Keep a running count of the number of non-lazy callbacks posted |
| 2104 | * on this CPU. This running counter (which is never decremented) allows |
| 2105 | * rcu_prepare_for_idle() to detect when something out of the idle loop |
| 2106 | * posts a callback, even if an equal number of callbacks are invoked. |
| 2107 | * Of course, callbacks should only be posted from within a trace event |
| 2108 | * designed to be called from idle or from within RCU_NONIDLE(). |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 2109 | */ |
| 2110 | static void rcu_idle_count_callbacks_posted(void) |
| 2111 | { |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2112 | __this_cpu_add(rcu_dynticks.nonlazy_posted, 1); |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 2113 | } |
| 2114 | |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 2115 | #endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 2116 | |
| 2117 | #ifdef CONFIG_RCU_CPU_STALL_INFO |
| 2118 | |
| 2119 | #ifdef CONFIG_RCU_FAST_NO_HZ |
| 2120 | |
| 2121 | static void print_cpu_stall_fast_no_hz(char *cp, int cpu) |
| 2122 | { |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2123 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); |
| 2124 | struct timer_list *tltp = &rdtp->idle_gp_timer; |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 2125 | |
Paul E. McKenney | 2ee3dc8 | 2012-02-23 17:13:19 -0800 | [diff] [blame] | 2126 | sprintf(cp, "drain=%d %c timer=%lu", |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 2127 | rdtp->dyntick_drain, |
| 2128 | rdtp->dyntick_holdoff == jiffies ? 'H' : '.', |
Paul E. McKenney | 2ee3dc8 | 2012-02-23 17:13:19 -0800 | [diff] [blame] | 2129 | timer_pending(tltp) ? tltp->expires - jiffies : -1); |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 2130 | } |
| 2131 | |
| 2132 | #else /* #ifdef CONFIG_RCU_FAST_NO_HZ */ |
| 2133 | |
| 2134 | static void print_cpu_stall_fast_no_hz(char *cp, int cpu) |
| 2135 | { |
Carsten Emde | 1c17e4d | 2012-06-19 10:43:16 +0200 | [diff] [blame] | 2136 | *cp = '\0'; |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 2137 | } |
| 2138 | |
| 2139 | #endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */ |
| 2140 | |
| 2141 | /* Initiate the stall-info list. */ |
| 2142 | static void print_cpu_stall_info_begin(void) |
| 2143 | { |
| 2144 | printk(KERN_CONT "\n"); |
| 2145 | } |
| 2146 | |
| 2147 | /* |
| 2148 | * Print out diagnostic information for the specified stalled CPU. |
| 2149 | * |
| 2150 | * If the specified CPU is aware of the current RCU grace period |
| 2151 | * (flavor specified by rsp), then print the number of scheduling |
| 2152 | * clock interrupts the CPU has taken during the time that it has |
| 2153 | * been aware. Otherwise, print the number of RCU grace periods |
| 2154 | * that this CPU is ignorant of, for example, "1" if the CPU was |
| 2155 | * aware of the previous grace period. |
| 2156 | * |
| 2157 | * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info. |
| 2158 | */ |
| 2159 | static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) |
| 2160 | { |
| 2161 | char fast_no_hz[72]; |
| 2162 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
| 2163 | struct rcu_dynticks *rdtp = rdp->dynticks; |
| 2164 | char *ticks_title; |
| 2165 | unsigned long ticks_value; |
| 2166 | |
| 2167 | if (rsp->gpnum == rdp->gpnum) { |
| 2168 | ticks_title = "ticks this GP"; |
| 2169 | ticks_value = rdp->ticks_this_gp; |
| 2170 | } else { |
| 2171 | ticks_title = "GPs behind"; |
| 2172 | ticks_value = rsp->gpnum - rdp->gpnum; |
| 2173 | } |
| 2174 | print_cpu_stall_fast_no_hz(fast_no_hz, cpu); |
| 2175 | printk(KERN_ERR "\t%d: (%lu %s) idle=%03x/%llx/%d %s\n", |
| 2176 | cpu, ticks_value, ticks_title, |
| 2177 | atomic_read(&rdtp->dynticks) & 0xfff, |
| 2178 | rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting, |
| 2179 | fast_no_hz); |
| 2180 | } |
| 2181 | |
| 2182 | /* Terminate the stall-info list. */ |
| 2183 | static void print_cpu_stall_info_end(void) |
| 2184 | { |
| 2185 | printk(KERN_ERR "\t"); |
| 2186 | } |
| 2187 | |
| 2188 | /* Zero ->ticks_this_gp for all flavors of RCU. */ |
| 2189 | static void zero_cpu_stall_ticks(struct rcu_data *rdp) |
| 2190 | { |
| 2191 | rdp->ticks_this_gp = 0; |
| 2192 | } |
| 2193 | |
| 2194 | /* Increment ->ticks_this_gp for all flavors of RCU. */ |
| 2195 | static void increment_cpu_stall_ticks(void) |
| 2196 | { |
| 2197 | __get_cpu_var(rcu_sched_data).ticks_this_gp++; |
| 2198 | __get_cpu_var(rcu_bh_data).ticks_this_gp++; |
| 2199 | #ifdef CONFIG_TREE_PREEMPT_RCU |
| 2200 | __get_cpu_var(rcu_preempt_data).ticks_this_gp++; |
| 2201 | #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ |
| 2202 | } |
| 2203 | |
| 2204 | #else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */ |
| 2205 | |
| 2206 | static void print_cpu_stall_info_begin(void) |
| 2207 | { |
| 2208 | printk(KERN_CONT " {"); |
| 2209 | } |
| 2210 | |
| 2211 | static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) |
| 2212 | { |
| 2213 | printk(KERN_CONT " %d", cpu); |
| 2214 | } |
| 2215 | |
| 2216 | static void print_cpu_stall_info_end(void) |
| 2217 | { |
| 2218 | printk(KERN_CONT "} "); |
| 2219 | } |
| 2220 | |
| 2221 | static void zero_cpu_stall_ticks(struct rcu_data *rdp) |
| 2222 | { |
| 2223 | } |
| 2224 | |
| 2225 | static void increment_cpu_stall_ticks(void) |
| 2226 | { |
| 2227 | } |
| 2228 | |
| 2229 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */ |