Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 1 | /* |
| 2 | * Read-Copy Update mechanism for mutual exclusion |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or modify |
| 5 | * it under the terms of the GNU General Public License as published by |
| 6 | * the Free Software Foundation; either version 2 of the License, or |
| 7 | * (at your option) any later version. |
| 8 | * |
| 9 | * This program is distributed in the hope that it will be useful, |
| 10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 12 | * GNU General Public License for more details. |
| 13 | * |
| 14 | * You should have received a copy of the GNU General Public License |
| 15 | * along with this program; if not, write to the Free Software |
| 16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 17 | * |
| 18 | * Copyright IBM Corporation, 2001 |
| 19 | * |
| 20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> |
| 21 | * Manfred Spraul <manfred@colorfullife.com> |
| 22 | * |
| 23 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
| 24 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
| 25 | * Papers: |
| 26 | * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf |
| 27 | * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) |
| 28 | * |
| 29 | * For detailed explanation of Read-Copy Update mechanism see - |
| 30 | * Documentation/RCU |
| 31 | * |
| 32 | */ |
| 33 | #include <linux/types.h> |
| 34 | #include <linux/kernel.h> |
| 35 | #include <linux/init.h> |
| 36 | #include <linux/spinlock.h> |
| 37 | #include <linux/smp.h> |
| 38 | #include <linux/rcupdate.h> |
| 39 | #include <linux/interrupt.h> |
| 40 | #include <linux/sched.h> |
| 41 | #include <asm/atomic.h> |
| 42 | #include <linux/bitops.h> |
| 43 | #include <linux/module.h> |
| 44 | #include <linux/completion.h> |
| 45 | #include <linux/moduleparam.h> |
| 46 | #include <linux/percpu.h> |
| 47 | #include <linux/notifier.h> |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 48 | #include <linux/cpu.h> |
| 49 | #include <linux/mutex.h> |
Paul E. McKenney | 67182ae | 2008-08-10 18:35:38 -0700 | [diff] [blame] | 50 | #include <linux/time.h> |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 51 | |
| 52 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| 53 | static struct lock_class_key rcu_lock_key; |
| 54 | struct lockdep_map rcu_lock_map = |
| 55 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); |
| 56 | EXPORT_SYMBOL_GPL(rcu_lock_map); |
| 57 | #endif |
| 58 | |
| 59 | |
| 60 | /* Definition for rcupdate control block. */ |
| 61 | static struct rcu_ctrlblk rcu_ctrlblk = { |
| 62 | .cur = -300, |
| 63 | .completed = -300, |
Lai Jiangshan | 3cac97c | 2008-07-06 17:23:55 +0800 | [diff] [blame] | 64 | .pending = -300, |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 65 | .lock = __SPIN_LOCK_UNLOCKED(&rcu_ctrlblk.lock), |
Rusty Russell | bd232f9 | 2009-01-01 10:12:26 +1030 | [diff] [blame] | 66 | .cpumask = CPU_BITS_NONE, |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 67 | }; |
Ingo Molnar | b1f77b0 | 2009-03-13 03:20:49 +0100 | [diff] [blame] | 68 | |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 69 | static struct rcu_ctrlblk rcu_bh_ctrlblk = { |
| 70 | .cur = -300, |
| 71 | .completed = -300, |
Lai Jiangshan | 3cac97c | 2008-07-06 17:23:55 +0800 | [diff] [blame] | 72 | .pending = -300, |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 73 | .lock = __SPIN_LOCK_UNLOCKED(&rcu_bh_ctrlblk.lock), |
Rusty Russell | bd232f9 | 2009-01-01 10:12:26 +1030 | [diff] [blame] | 74 | .cpumask = CPU_BITS_NONE, |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 75 | }; |
| 76 | |
Ingo Molnar | b1f77b0 | 2009-03-13 03:20:49 +0100 | [diff] [blame] | 77 | static DEFINE_PER_CPU(struct rcu_data, rcu_data); |
| 78 | static DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); |
| 79 | |
| 80 | /* |
| 81 | * Increment the quiescent state counter. |
| 82 | * The counter is a bit degenerated: We do not need to know |
| 83 | * how many quiescent states passed, just if there was at least |
| 84 | * one since the start of the grace period. Thus just a flag. |
| 85 | */ |
| 86 | void rcu_qsctr_inc(int cpu) |
| 87 | { |
| 88 | struct rcu_data *rdp = &per_cpu(rcu_data, cpu); |
| 89 | rdp->passed_quiesc = 1; |
| 90 | } |
| 91 | |
| 92 | void rcu_bh_qsctr_inc(int cpu) |
| 93 | { |
| 94 | struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); |
| 95 | rdp->passed_quiesc = 1; |
| 96 | } |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 97 | |
| 98 | static int blimit = 10; |
| 99 | static int qhimark = 10000; |
| 100 | static int qlowmark = 100; |
| 101 | |
| 102 | #ifdef CONFIG_SMP |
| 103 | static void force_quiescent_state(struct rcu_data *rdp, |
| 104 | struct rcu_ctrlblk *rcp) |
| 105 | { |
| 106 | int cpu; |
Paul E. McKenney | eff9b71 | 2008-08-18 17:51:08 -0700 | [diff] [blame] | 107 | unsigned long flags; |
| 108 | |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 109 | set_need_resched(); |
Paul E. McKenney | eff9b71 | 2008-08-18 17:51:08 -0700 | [diff] [blame] | 110 | spin_lock_irqsave(&rcp->lock, flags); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 111 | if (unlikely(!rcp->signaled)) { |
| 112 | rcp->signaled = 1; |
| 113 | /* |
| 114 | * Don't send IPI to itself. With irqs disabled, |
| 115 | * rdp->cpu is the current cpu. |
Gautham R Shenoy | 8558f8f | 2008-06-27 10:17:38 +0530 | [diff] [blame] | 116 | * |
Rusty Russell | bd232f9 | 2009-01-01 10:12:26 +1030 | [diff] [blame] | 117 | * cpu_online_mask is updated by the _cpu_down() |
Rusty Russell | 9b1a4d3 | 2008-07-28 12:16:30 -0500 | [diff] [blame] | 118 | * using __stop_machine(). Since we're in irqs disabled |
| 119 | * section, __stop_machine() is not exectuting, hence |
Rusty Russell | bd232f9 | 2009-01-01 10:12:26 +1030 | [diff] [blame] | 120 | * the cpu_online_mask is stable. |
Gautham R Shenoy | 8558f8f | 2008-06-27 10:17:38 +0530 | [diff] [blame] | 121 | * |
| 122 | * However, a cpu might have been offlined _just_ before |
| 123 | * we disabled irqs while entering here. |
| 124 | * And rcu subsystem might not yet have handled the CPU_DEAD |
| 125 | * notification, leading to the offlined cpu's bit |
| 126 | * being set in the rcp->cpumask. |
| 127 | * |
Rusty Russell | bd232f9 | 2009-01-01 10:12:26 +1030 | [diff] [blame] | 128 | * Hence cpumask = (rcp->cpumask & cpu_online_mask) to prevent |
Gautham R Shenoy | 8558f8f | 2008-06-27 10:17:38 +0530 | [diff] [blame] | 129 | * sending smp_reschedule() to an offlined CPU. |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 130 | */ |
Rusty Russell | bd232f9 | 2009-01-01 10:12:26 +1030 | [diff] [blame] | 131 | for_each_cpu_and(cpu, |
| 132 | to_cpumask(rcp->cpumask), cpu_online_mask) { |
| 133 | if (cpu != rdp->cpu) |
| 134 | smp_send_reschedule(cpu); |
| 135 | } |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 136 | } |
Paul E. McKenney | eff9b71 | 2008-08-18 17:51:08 -0700 | [diff] [blame] | 137 | spin_unlock_irqrestore(&rcp->lock, flags); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 138 | } |
| 139 | #else |
| 140 | static inline void force_quiescent_state(struct rcu_data *rdp, |
| 141 | struct rcu_ctrlblk *rcp) |
| 142 | { |
| 143 | set_need_resched(); |
| 144 | } |
| 145 | #endif |
| 146 | |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 147 | static void __call_rcu(struct rcu_head *head, struct rcu_ctrlblk *rcp, |
| 148 | struct rcu_data *rdp) |
| 149 | { |
| 150 | long batch; |
Paul E. McKenney | 1f7b94c | 2008-08-05 09:21:44 -0700 | [diff] [blame] | 151 | |
| 152 | head->next = NULL; |
| 153 | smp_mb(); /* Read of rcu->cur must happen after any change by caller. */ |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 154 | |
| 155 | /* |
| 156 | * Determine the batch number of this callback. |
| 157 | * |
| 158 | * Using ACCESS_ONCE to avoid the following error when gcc eliminates |
| 159 | * local variable "batch" and emits codes like this: |
| 160 | * 1) rdp->batch = rcp->cur + 1 # gets old value |
| 161 | * ...... |
| 162 | * 2)rcu_batch_after(rcp->cur + 1, rdp->batch) # gets new value |
| 163 | * then [*nxttail[0], *nxttail[1]) may contain callbacks |
| 164 | * that batch# = rdp->batch, see the comment of struct rcu_data. |
| 165 | */ |
| 166 | batch = ACCESS_ONCE(rcp->cur) + 1; |
| 167 | |
| 168 | if (rdp->nxtlist && rcu_batch_after(batch, rdp->batch)) { |
| 169 | /* process callbacks */ |
| 170 | rdp->nxttail[0] = rdp->nxttail[1]; |
| 171 | rdp->nxttail[1] = rdp->nxttail[2]; |
| 172 | if (rcu_batch_after(batch - 1, rdp->batch)) |
| 173 | rdp->nxttail[0] = rdp->nxttail[2]; |
| 174 | } |
| 175 | |
| 176 | rdp->batch = batch; |
| 177 | *rdp->nxttail[2] = head; |
| 178 | rdp->nxttail[2] = &head->next; |
| 179 | |
| 180 | if (unlikely(++rdp->qlen > qhimark)) { |
| 181 | rdp->blimit = INT_MAX; |
| 182 | force_quiescent_state(rdp, &rcu_ctrlblk); |
| 183 | } |
| 184 | } |
| 185 | |
Paul E. McKenney | 2133b5d | 2008-10-02 16:06:39 -0700 | [diff] [blame] | 186 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
| 187 | |
| 188 | static void record_gp_stall_check_time(struct rcu_ctrlblk *rcp) |
| 189 | { |
| 190 | rcp->gp_start = jiffies; |
| 191 | rcp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK; |
| 192 | } |
| 193 | |
| 194 | static void print_other_cpu_stall(struct rcu_ctrlblk *rcp) |
| 195 | { |
| 196 | int cpu; |
| 197 | long delta; |
| 198 | unsigned long flags; |
| 199 | |
| 200 | /* Only let one CPU complain about others per time interval. */ |
| 201 | |
| 202 | spin_lock_irqsave(&rcp->lock, flags); |
| 203 | delta = jiffies - rcp->jiffies_stall; |
| 204 | if (delta < 2 || rcp->cur != rcp->completed) { |
| 205 | spin_unlock_irqrestore(&rcp->lock, flags); |
| 206 | return; |
| 207 | } |
| 208 | rcp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK; |
| 209 | spin_unlock_irqrestore(&rcp->lock, flags); |
| 210 | |
| 211 | /* OK, time to rat on our buddy... */ |
| 212 | |
Ingo Molnar | be19ef8 | 2008-11-03 14:35:12 +0100 | [diff] [blame] | 213 | printk(KERN_ERR "INFO: RCU detected CPU stalls:"); |
Paul E. McKenney | 2133b5d | 2008-10-02 16:06:39 -0700 | [diff] [blame] | 214 | for_each_possible_cpu(cpu) { |
Rusty Russell | bd232f9 | 2009-01-01 10:12:26 +1030 | [diff] [blame] | 215 | if (cpumask_test_cpu(cpu, to_cpumask(rcp->cpumask))) |
Paul E. McKenney | 2133b5d | 2008-10-02 16:06:39 -0700 | [diff] [blame] | 216 | printk(" %d", cpu); |
| 217 | } |
| 218 | printk(" (detected by %d, t=%ld jiffies)\n", |
| 219 | smp_processor_id(), (long)(jiffies - rcp->gp_start)); |
| 220 | } |
| 221 | |
| 222 | static void print_cpu_stall(struct rcu_ctrlblk *rcp) |
| 223 | { |
| 224 | unsigned long flags; |
| 225 | |
Ingo Molnar | be19ef8 | 2008-11-03 14:35:12 +0100 | [diff] [blame] | 226 | printk(KERN_ERR "INFO: RCU detected CPU %d stall (t=%lu/%lu jiffies)\n", |
Paul E. McKenney | 2133b5d | 2008-10-02 16:06:39 -0700 | [diff] [blame] | 227 | smp_processor_id(), jiffies, |
| 228 | jiffies - rcp->gp_start); |
| 229 | dump_stack(); |
| 230 | spin_lock_irqsave(&rcp->lock, flags); |
| 231 | if ((long)(jiffies - rcp->jiffies_stall) >= 0) |
| 232 | rcp->jiffies_stall = |
| 233 | jiffies + RCU_SECONDS_TILL_STALL_RECHECK; |
| 234 | spin_unlock_irqrestore(&rcp->lock, flags); |
| 235 | set_need_resched(); /* kick ourselves to get things going. */ |
| 236 | } |
| 237 | |
| 238 | static void check_cpu_stall(struct rcu_ctrlblk *rcp) |
| 239 | { |
| 240 | long delta; |
| 241 | |
| 242 | delta = jiffies - rcp->jiffies_stall; |
Rusty Russell | bd232f9 | 2009-01-01 10:12:26 +1030 | [diff] [blame] | 243 | if (cpumask_test_cpu(smp_processor_id(), to_cpumask(rcp->cpumask)) && |
| 244 | delta >= 0) { |
Paul E. McKenney | 2133b5d | 2008-10-02 16:06:39 -0700 | [diff] [blame] | 245 | |
| 246 | /* We haven't checked in, so go dump stack. */ |
| 247 | print_cpu_stall(rcp); |
| 248 | |
| 249 | } else if (rcp->cur != rcp->completed && delta >= 2) { |
| 250 | |
| 251 | /* They had two seconds to dump stack, so complain. */ |
| 252 | print_other_cpu_stall(rcp); |
| 253 | } |
| 254 | } |
| 255 | |
| 256 | #else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
| 257 | |
| 258 | static void record_gp_stall_check_time(struct rcu_ctrlblk *rcp) |
| 259 | { |
| 260 | } |
| 261 | |
Ingo Molnar | 2ec2b48 | 2008-10-03 10:41:00 +0200 | [diff] [blame] | 262 | static inline void check_cpu_stall(struct rcu_ctrlblk *rcp) |
Paul E. McKenney | 2133b5d | 2008-10-02 16:06:39 -0700 | [diff] [blame] | 263 | { |
| 264 | } |
| 265 | |
| 266 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
| 267 | |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 268 | /** |
| 269 | * call_rcu - Queue an RCU callback for invocation after a grace period. |
| 270 | * @head: structure to be used for queueing the RCU updates. |
| 271 | * @func: actual update function to be invoked after the grace period |
| 272 | * |
| 273 | * The update function will be invoked some time after a full grace |
| 274 | * period elapses, in other words after all currently executing RCU |
| 275 | * read-side critical sections have completed. RCU read-side critical |
| 276 | * sections are delimited by rcu_read_lock() and rcu_read_unlock(), |
| 277 | * and may be nested. |
| 278 | */ |
| 279 | void call_rcu(struct rcu_head *head, |
| 280 | void (*func)(struct rcu_head *rcu)) |
| 281 | { |
| 282 | unsigned long flags; |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 283 | |
| 284 | head->func = func; |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 285 | local_irq_save(flags); |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 286 | __call_rcu(head, &rcu_ctrlblk, &__get_cpu_var(rcu_data)); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 287 | local_irq_restore(flags); |
| 288 | } |
| 289 | EXPORT_SYMBOL_GPL(call_rcu); |
| 290 | |
| 291 | /** |
| 292 | * call_rcu_bh - Queue an RCU for invocation after a quicker grace period. |
| 293 | * @head: structure to be used for queueing the RCU updates. |
| 294 | * @func: actual update function to be invoked after the grace period |
| 295 | * |
| 296 | * The update function will be invoked some time after a full grace |
| 297 | * period elapses, in other words after all currently executing RCU |
| 298 | * read-side critical sections have completed. call_rcu_bh() assumes |
| 299 | * that the read-side critical sections end on completion of a softirq |
| 300 | * handler. This means that read-side critical sections in process |
| 301 | * context must not be interrupted by softirqs. This interface is to be |
| 302 | * used when most of the read-side critical sections are in softirq context. |
| 303 | * RCU read-side critical sections are delimited by rcu_read_lock() and |
| 304 | * rcu_read_unlock(), * if in interrupt context or rcu_read_lock_bh() |
| 305 | * and rcu_read_unlock_bh(), if in process context. These may be nested. |
| 306 | */ |
| 307 | void call_rcu_bh(struct rcu_head *head, |
| 308 | void (*func)(struct rcu_head *rcu)) |
| 309 | { |
| 310 | unsigned long flags; |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 311 | |
| 312 | head->func = func; |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 313 | local_irq_save(flags); |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 314 | __call_rcu(head, &rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data)); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 315 | local_irq_restore(flags); |
| 316 | } |
| 317 | EXPORT_SYMBOL_GPL(call_rcu_bh); |
| 318 | |
| 319 | /* |
| 320 | * Return the number of RCU batches processed thus far. Useful |
| 321 | * for debug and statistics. |
| 322 | */ |
| 323 | long rcu_batches_completed(void) |
| 324 | { |
| 325 | return rcu_ctrlblk.completed; |
| 326 | } |
| 327 | EXPORT_SYMBOL_GPL(rcu_batches_completed); |
| 328 | |
| 329 | /* |
| 330 | * Return the number of RCU batches processed thus far. Useful |
| 331 | * for debug and statistics. |
| 332 | */ |
| 333 | long rcu_batches_completed_bh(void) |
| 334 | { |
| 335 | return rcu_bh_ctrlblk.completed; |
| 336 | } |
| 337 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); |
| 338 | |
| 339 | /* Raises the softirq for processing rcu_callbacks. */ |
| 340 | static inline void raise_rcu_softirq(void) |
| 341 | { |
| 342 | raise_softirq(RCU_SOFTIRQ); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 343 | } |
| 344 | |
| 345 | /* |
| 346 | * Invoke the completed RCU callbacks. They are expected to be in |
| 347 | * a per-cpu list. |
| 348 | */ |
| 349 | static void rcu_do_batch(struct rcu_data *rdp) |
| 350 | { |
Paul E. McKenney | 275a89bd | 2008-08-21 06:14:55 -0700 | [diff] [blame] | 351 | unsigned long flags; |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 352 | struct rcu_head *next, *list; |
| 353 | int count = 0; |
| 354 | |
| 355 | list = rdp->donelist; |
| 356 | while (list) { |
| 357 | next = list->next; |
| 358 | prefetch(next); |
| 359 | list->func(list); |
| 360 | list = next; |
| 361 | if (++count >= rdp->blimit) |
| 362 | break; |
| 363 | } |
| 364 | rdp->donelist = list; |
| 365 | |
Paul E. McKenney | 275a89bd | 2008-08-21 06:14:55 -0700 | [diff] [blame] | 366 | local_irq_save(flags); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 367 | rdp->qlen -= count; |
Paul E. McKenney | 275a89bd | 2008-08-21 06:14:55 -0700 | [diff] [blame] | 368 | local_irq_restore(flags); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 369 | if (rdp->blimit == INT_MAX && rdp->qlen <= qlowmark) |
| 370 | rdp->blimit = blimit; |
| 371 | |
| 372 | if (!rdp->donelist) |
| 373 | rdp->donetail = &rdp->donelist; |
| 374 | else |
| 375 | raise_rcu_softirq(); |
| 376 | } |
| 377 | |
| 378 | /* |
| 379 | * Grace period handling: |
| 380 | * The grace period handling consists out of two steps: |
| 381 | * - A new grace period is started. |
| 382 | * This is done by rcu_start_batch. The start is not broadcasted to |
| 383 | * all cpus, they must pick this up by comparing rcp->cur with |
| 384 | * rdp->quiescbatch. All cpus are recorded in the |
| 385 | * rcu_ctrlblk.cpumask bitmap. |
| 386 | * - All cpus must go through a quiescent state. |
| 387 | * Since the start of the grace period is not broadcasted, at least two |
| 388 | * calls to rcu_check_quiescent_state are required: |
| 389 | * The first call just notices that a new grace period is running. The |
| 390 | * following calls check if there was a quiescent state since the beginning |
| 391 | * of the grace period. If so, it updates rcu_ctrlblk.cpumask. If |
| 392 | * the bitmap is empty, then the grace period is completed. |
| 393 | * rcu_check_quiescent_state calls rcu_start_batch(0) to start the next grace |
| 394 | * period (if necessary). |
| 395 | */ |
Paul E. McKenney | 67182ae | 2008-08-10 18:35:38 -0700 | [diff] [blame] | 396 | |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 397 | /* |
| 398 | * Register a new batch of callbacks, and start it up if there is currently no |
| 399 | * active batch and the batch to be registered has not already occurred. |
| 400 | * Caller must hold rcu_ctrlblk.lock. |
| 401 | */ |
| 402 | static void rcu_start_batch(struct rcu_ctrlblk *rcp) |
| 403 | { |
Lai Jiangshan | 3cac97c | 2008-07-06 17:23:55 +0800 | [diff] [blame] | 404 | if (rcp->cur != rcp->pending && |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 405 | rcp->completed == rcp->cur) { |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 406 | rcp->cur++; |
Paul E. McKenney | 2133b5d | 2008-10-02 16:06:39 -0700 | [diff] [blame] | 407 | record_gp_stall_check_time(rcp); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 408 | |
| 409 | /* |
| 410 | * Accessing nohz_cpu_mask before incrementing rcp->cur needs a |
| 411 | * Barrier Otherwise it can cause tickless idle CPUs to be |
| 412 | * included in rcp->cpumask, which will extend graceperiods |
| 413 | * unnecessarily. |
| 414 | */ |
| 415 | smp_mb(); |
Ingo Molnar | 263ec64 | 2009-01-03 13:16:09 +0100 | [diff] [blame] | 416 | cpumask_andnot(to_cpumask(rcp->cpumask), |
| 417 | cpu_online_mask, nohz_cpu_mask); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 418 | |
| 419 | rcp->signaled = 0; |
| 420 | } |
| 421 | } |
| 422 | |
| 423 | /* |
| 424 | * cpu went through a quiescent state since the beginning of the grace period. |
| 425 | * Clear it from the cpu mask and complete the grace period if it was the last |
| 426 | * cpu. Start another grace period if someone has further entries pending |
| 427 | */ |
| 428 | static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp) |
| 429 | { |
Rusty Russell | bd232f9 | 2009-01-01 10:12:26 +1030 | [diff] [blame] | 430 | cpumask_clear_cpu(cpu, to_cpumask(rcp->cpumask)); |
| 431 | if (cpumask_empty(to_cpumask(rcp->cpumask))) { |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 432 | /* batch completed ! */ |
| 433 | rcp->completed = rcp->cur; |
| 434 | rcu_start_batch(rcp); |
| 435 | } |
| 436 | } |
| 437 | |
| 438 | /* |
| 439 | * Check if the cpu has gone through a quiescent state (say context |
| 440 | * switch). If so and if it already hasn't done so in this RCU |
| 441 | * quiescent cycle, then indicate that it has done so. |
| 442 | */ |
| 443 | static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp, |
| 444 | struct rcu_data *rdp) |
| 445 | { |
Paul E. McKenney | eff9b71 | 2008-08-18 17:51:08 -0700 | [diff] [blame] | 446 | unsigned long flags; |
| 447 | |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 448 | if (rdp->quiescbatch != rcp->cur) { |
| 449 | /* start new grace period: */ |
| 450 | rdp->qs_pending = 1; |
| 451 | rdp->passed_quiesc = 0; |
| 452 | rdp->quiescbatch = rcp->cur; |
| 453 | return; |
| 454 | } |
| 455 | |
| 456 | /* Grace period already completed for this cpu? |
| 457 | * qs_pending is checked instead of the actual bitmap to avoid |
| 458 | * cacheline trashing. |
| 459 | */ |
| 460 | if (!rdp->qs_pending) |
| 461 | return; |
| 462 | |
| 463 | /* |
| 464 | * Was there a quiescent state since the beginning of the grace |
| 465 | * period? If no, then exit and wait for the next call. |
| 466 | */ |
| 467 | if (!rdp->passed_quiesc) |
| 468 | return; |
| 469 | rdp->qs_pending = 0; |
| 470 | |
Paul E. McKenney | eff9b71 | 2008-08-18 17:51:08 -0700 | [diff] [blame] | 471 | spin_lock_irqsave(&rcp->lock, flags); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 472 | /* |
| 473 | * rdp->quiescbatch/rcp->cur and the cpu bitmap can come out of sync |
| 474 | * during cpu startup. Ignore the quiescent state. |
| 475 | */ |
| 476 | if (likely(rdp->quiescbatch == rcp->cur)) |
| 477 | cpu_quiet(rdp->cpu, rcp); |
| 478 | |
Paul E. McKenney | eff9b71 | 2008-08-18 17:51:08 -0700 | [diff] [blame] | 479 | spin_unlock_irqrestore(&rcp->lock, flags); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 480 | } |
| 481 | |
| 482 | |
| 483 | #ifdef CONFIG_HOTPLUG_CPU |
| 484 | |
| 485 | /* warning! helper for rcu_offline_cpu. do not use elsewhere without reviewing |
| 486 | * locking requirements, the list it's pulling from has to belong to a cpu |
| 487 | * which is dead and hence not processing interrupts. |
| 488 | */ |
| 489 | static void rcu_move_batch(struct rcu_data *this_rdp, struct rcu_head *list, |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 490 | struct rcu_head **tail, long batch) |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 491 | { |
Paul E. McKenney | 275a89bd | 2008-08-21 06:14:55 -0700 | [diff] [blame] | 492 | unsigned long flags; |
| 493 | |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 494 | if (list) { |
Paul E. McKenney | 275a89bd | 2008-08-21 06:14:55 -0700 | [diff] [blame] | 495 | local_irq_save(flags); |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 496 | this_rdp->batch = batch; |
| 497 | *this_rdp->nxttail[2] = list; |
| 498 | this_rdp->nxttail[2] = tail; |
Paul E. McKenney | 275a89bd | 2008-08-21 06:14:55 -0700 | [diff] [blame] | 499 | local_irq_restore(flags); |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 500 | } |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 501 | } |
| 502 | |
| 503 | static void __rcu_offline_cpu(struct rcu_data *this_rdp, |
| 504 | struct rcu_ctrlblk *rcp, struct rcu_data *rdp) |
| 505 | { |
Paul E. McKenney | eff9b71 | 2008-08-18 17:51:08 -0700 | [diff] [blame] | 506 | unsigned long flags; |
| 507 | |
Paul E. McKenney | 1f7b94c | 2008-08-05 09:21:44 -0700 | [diff] [blame] | 508 | /* |
| 509 | * if the cpu going offline owns the grace period |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 510 | * we can block indefinitely waiting for it, so flush |
| 511 | * it here |
| 512 | */ |
Paul E. McKenney | eff9b71 | 2008-08-18 17:51:08 -0700 | [diff] [blame] | 513 | spin_lock_irqsave(&rcp->lock, flags); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 514 | if (rcp->cur != rcp->completed) |
| 515 | cpu_quiet(rdp->cpu, rcp); |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 516 | rcu_move_batch(this_rdp, rdp->donelist, rdp->donetail, rcp->cur + 1); |
| 517 | rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail[2], rcp->cur + 1); |
Paul E. McKenney | eff9b71 | 2008-08-18 17:51:08 -0700 | [diff] [blame] | 518 | spin_unlock(&rcp->lock); |
Lai Jiangshan | 199a952 | 2008-06-26 10:06:43 +0800 | [diff] [blame] | 519 | |
Lai Jiangshan | 199a952 | 2008-06-26 10:06:43 +0800 | [diff] [blame] | 520 | this_rdp->qlen += rdp->qlen; |
Paul E. McKenney | eff9b71 | 2008-08-18 17:51:08 -0700 | [diff] [blame] | 521 | local_irq_restore(flags); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 522 | } |
| 523 | |
| 524 | static void rcu_offline_cpu(int cpu) |
| 525 | { |
| 526 | struct rcu_data *this_rdp = &get_cpu_var(rcu_data); |
| 527 | struct rcu_data *this_bh_rdp = &get_cpu_var(rcu_bh_data); |
| 528 | |
| 529 | __rcu_offline_cpu(this_rdp, &rcu_ctrlblk, |
| 530 | &per_cpu(rcu_data, cpu)); |
| 531 | __rcu_offline_cpu(this_bh_rdp, &rcu_bh_ctrlblk, |
| 532 | &per_cpu(rcu_bh_data, cpu)); |
| 533 | put_cpu_var(rcu_data); |
| 534 | put_cpu_var(rcu_bh_data); |
| 535 | } |
| 536 | |
| 537 | #else |
| 538 | |
| 539 | static void rcu_offline_cpu(int cpu) |
| 540 | { |
| 541 | } |
| 542 | |
| 543 | #endif |
| 544 | |
| 545 | /* |
| 546 | * This does the RCU processing work from softirq context. |
| 547 | */ |
| 548 | static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp, |
| 549 | struct rcu_data *rdp) |
| 550 | { |
Paul E. McKenney | 275a89bd | 2008-08-21 06:14:55 -0700 | [diff] [blame] | 551 | unsigned long flags; |
Paul E. McKenney | 1f7b94c | 2008-08-05 09:21:44 -0700 | [diff] [blame] | 552 | long completed_snap; |
| 553 | |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 554 | if (rdp->nxtlist) { |
Paul E. McKenney | 275a89bd | 2008-08-21 06:14:55 -0700 | [diff] [blame] | 555 | local_irq_save(flags); |
Paul E. McKenney | 1f7b94c | 2008-08-05 09:21:44 -0700 | [diff] [blame] | 556 | completed_snap = ACCESS_ONCE(rcp->completed); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 557 | |
| 558 | /* |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 559 | * move the other grace-period-completed entries to |
| 560 | * [rdp->nxtlist, *rdp->nxttail[0]) temporarily |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 561 | */ |
Paul E. McKenney | 1f7b94c | 2008-08-05 09:21:44 -0700 | [diff] [blame] | 562 | if (!rcu_batch_before(completed_snap, rdp->batch)) |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 563 | rdp->nxttail[0] = rdp->nxttail[1] = rdp->nxttail[2]; |
Paul E. McKenney | 1f7b94c | 2008-08-05 09:21:44 -0700 | [diff] [blame] | 564 | else if (!rcu_batch_before(completed_snap, rdp->batch - 1)) |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 565 | rdp->nxttail[0] = rdp->nxttail[1]; |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 566 | |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 567 | /* |
| 568 | * the grace period for entries in |
| 569 | * [rdp->nxtlist, *rdp->nxttail[0]) has completed and |
| 570 | * move these entries to donelist |
| 571 | */ |
| 572 | if (rdp->nxttail[0] != &rdp->nxtlist) { |
| 573 | *rdp->donetail = rdp->nxtlist; |
| 574 | rdp->donetail = rdp->nxttail[0]; |
| 575 | rdp->nxtlist = *rdp->nxttail[0]; |
| 576 | *rdp->donetail = NULL; |
| 577 | |
| 578 | if (rdp->nxttail[1] == rdp->nxttail[0]) |
| 579 | rdp->nxttail[1] = &rdp->nxtlist; |
| 580 | if (rdp->nxttail[2] == rdp->nxttail[0]) |
| 581 | rdp->nxttail[2] = &rdp->nxtlist; |
| 582 | rdp->nxttail[0] = &rdp->nxtlist; |
| 583 | } |
| 584 | |
Paul E. McKenney | 275a89bd | 2008-08-21 06:14:55 -0700 | [diff] [blame] | 585 | local_irq_restore(flags); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 586 | |
Lai Jiangshan | 3cac97c | 2008-07-06 17:23:55 +0800 | [diff] [blame] | 587 | if (rcu_batch_after(rdp->batch, rcp->pending)) { |
Harvey Harrison | 3a72dc8 | 2008-09-22 14:55:46 -0700 | [diff] [blame] | 588 | unsigned long flags2; |
Hiroshi Shimamoto | 0c925d7 | 2008-08-18 21:49:51 -0700 | [diff] [blame] | 589 | |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 590 | /* and start it/schedule start if it's a new batch */ |
Harvey Harrison | 3a72dc8 | 2008-09-22 14:55:46 -0700 | [diff] [blame] | 591 | spin_lock_irqsave(&rcp->lock, flags2); |
Lai Jiangshan | 3cac97c | 2008-07-06 17:23:55 +0800 | [diff] [blame] | 592 | if (rcu_batch_after(rdp->batch, rcp->pending)) { |
| 593 | rcp->pending = rdp->batch; |
| 594 | rcu_start_batch(rcp); |
| 595 | } |
Harvey Harrison | 3a72dc8 | 2008-09-22 14:55:46 -0700 | [diff] [blame] | 596 | spin_unlock_irqrestore(&rcp->lock, flags2); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 597 | } |
| 598 | } |
| 599 | |
| 600 | rcu_check_quiescent_state(rcp, rdp); |
| 601 | if (rdp->donelist) |
| 602 | rcu_do_batch(rdp); |
| 603 | } |
| 604 | |
| 605 | static void rcu_process_callbacks(struct softirq_action *unused) |
| 606 | { |
Paul E. McKenney | 1f7b94c | 2008-08-05 09:21:44 -0700 | [diff] [blame] | 607 | /* |
| 608 | * Memory references from any prior RCU read-side critical sections |
| 609 | * executed by the interrupted code must be see before any RCU |
| 610 | * grace-period manupulations below. |
| 611 | */ |
| 612 | |
| 613 | smp_mb(); /* See above block comment. */ |
| 614 | |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 615 | __rcu_process_callbacks(&rcu_ctrlblk, &__get_cpu_var(rcu_data)); |
| 616 | __rcu_process_callbacks(&rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data)); |
Paul E. McKenney | 1f7b94c | 2008-08-05 09:21:44 -0700 | [diff] [blame] | 617 | |
| 618 | /* |
| 619 | * Memory references from any later RCU read-side critical sections |
| 620 | * executed by the interrupted code must be see after any RCU |
| 621 | * grace-period manupulations above. |
| 622 | */ |
| 623 | |
| 624 | smp_mb(); /* See above block comment. */ |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 625 | } |
| 626 | |
| 627 | static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp) |
| 628 | { |
Paul E. McKenney | 67182ae | 2008-08-10 18:35:38 -0700 | [diff] [blame] | 629 | /* Check for CPU stalls, if enabled. */ |
Paul E. McKenney | 2133b5d | 2008-10-02 16:06:39 -0700 | [diff] [blame] | 630 | check_cpu_stall(rcp); |
Paul E. McKenney | 67182ae | 2008-08-10 18:35:38 -0700 | [diff] [blame] | 631 | |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 632 | if (rdp->nxtlist) { |
Paul E. McKenney | 1f7b94c | 2008-08-05 09:21:44 -0700 | [diff] [blame] | 633 | long completed_snap = ACCESS_ONCE(rcp->completed); |
| 634 | |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 635 | /* |
| 636 | * This cpu has pending rcu entries and the grace period |
| 637 | * for them has completed. |
| 638 | */ |
Paul E. McKenney | 1f7b94c | 2008-08-05 09:21:44 -0700 | [diff] [blame] | 639 | if (!rcu_batch_before(completed_snap, rdp->batch)) |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 640 | return 1; |
Paul E. McKenney | 1f7b94c | 2008-08-05 09:21:44 -0700 | [diff] [blame] | 641 | if (!rcu_batch_before(completed_snap, rdp->batch - 1) && |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 642 | rdp->nxttail[0] != rdp->nxttail[1]) |
| 643 | return 1; |
| 644 | if (rdp->nxttail[0] != &rdp->nxtlist) |
| 645 | return 1; |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 646 | |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 647 | /* |
| 648 | * This cpu has pending rcu entries and the new batch |
| 649 | * for then hasn't been started nor scheduled start |
| 650 | */ |
| 651 | if (rcu_batch_after(rdp->batch, rcp->pending)) |
| 652 | return 1; |
| 653 | } |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 654 | |
| 655 | /* This cpu has finished callbacks to invoke */ |
| 656 | if (rdp->donelist) |
| 657 | return 1; |
| 658 | |
| 659 | /* The rcu core waits for a quiescent state from the cpu */ |
| 660 | if (rdp->quiescbatch != rcp->cur || rdp->qs_pending) |
| 661 | return 1; |
| 662 | |
| 663 | /* nothing to do */ |
| 664 | return 0; |
| 665 | } |
| 666 | |
| 667 | /* |
| 668 | * Check to see if there is any immediate RCU-related work to be done |
| 669 | * by the current CPU, returning 1 if so. This function is part of the |
| 670 | * RCU implementation; it is -not- an exported member of the RCU API. |
| 671 | */ |
| 672 | int rcu_pending(int cpu) |
| 673 | { |
| 674 | return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) || |
| 675 | __rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_data, cpu)); |
| 676 | } |
| 677 | |
| 678 | /* |
| 679 | * Check to see if any future RCU-related work will need to be done |
| 680 | * by the current CPU, even if none need be done immediately, returning |
| 681 | * 1 if so. This function is part of the RCU implementation; it is -not- |
| 682 | * an exported member of the RCU API. |
| 683 | */ |
| 684 | int rcu_needs_cpu(int cpu) |
| 685 | { |
| 686 | struct rcu_data *rdp = &per_cpu(rcu_data, cpu); |
| 687 | struct rcu_data *rdp_bh = &per_cpu(rcu_bh_data, cpu); |
| 688 | |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 689 | return !!rdp->nxtlist || !!rdp_bh->nxtlist || rcu_pending(cpu); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 690 | } |
| 691 | |
Paul E. McKenney | 1f7b94c | 2008-08-05 09:21:44 -0700 | [diff] [blame] | 692 | /* |
| 693 | * Top-level function driving RCU grace-period detection, normally |
| 694 | * invoked from the scheduler-clock interrupt. This function simply |
| 695 | * increments counters that are read only from softirq by this same |
| 696 | * CPU, so there are no memory barriers required. |
| 697 | */ |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 698 | void rcu_check_callbacks(int cpu, int user) |
| 699 | { |
| 700 | if (user || |
Paul E. McKenney | a682604 | 2009-02-25 18:03:42 -0800 | [diff] [blame] | 701 | (idle_cpu(cpu) && rcu_scheduler_active && |
| 702 | !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { |
Paul E. McKenney | 8db559b | 2008-05-12 21:21:05 +0200 | [diff] [blame] | 703 | |
| 704 | /* |
| 705 | * Get here if this CPU took its interrupt from user |
| 706 | * mode or from the idle loop, and if this is not a |
| 707 | * nested interrupt. In this case, the CPU is in |
| 708 | * a quiescent state, so count it. |
| 709 | * |
| 710 | * Also do a memory barrier. This is needed to handle |
| 711 | * the case where writes from a preempt-disable section |
| 712 | * of code get reordered into schedule() by this CPU's |
| 713 | * write buffer. The memory barrier makes sure that |
| 714 | * the rcu_qsctr_inc() and rcu_bh_qsctr_inc() are see |
| 715 | * by other CPUs to happen after any such write. |
| 716 | */ |
| 717 | |
| 718 | smp_mb(); /* See above block comment. */ |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 719 | rcu_qsctr_inc(cpu); |
| 720 | rcu_bh_qsctr_inc(cpu); |
Paul E. McKenney | 8db559b | 2008-05-12 21:21:05 +0200 | [diff] [blame] | 721 | |
| 722 | } else if (!in_softirq()) { |
| 723 | |
| 724 | /* |
| 725 | * Get here if this CPU did not take its interrupt from |
| 726 | * softirq, in other words, if it is not interrupting |
| 727 | * a rcu_bh read-side critical section. This is an _bh |
| 728 | * critical section, so count it. The memory barrier |
| 729 | * is needed for the same reason as is the above one. |
| 730 | */ |
| 731 | |
| 732 | smp_mb(); /* See above block comment. */ |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 733 | rcu_bh_qsctr_inc(cpu); |
Paul E. McKenney | 8db559b | 2008-05-12 21:21:05 +0200 | [diff] [blame] | 734 | } |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 735 | raise_rcu_softirq(); |
| 736 | } |
| 737 | |
Lai Jiangshan | e4fa4c9 | 2009-01-14 14:58:15 +0800 | [diff] [blame] | 738 | static void __cpuinit rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp, |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 739 | struct rcu_data *rdp) |
| 740 | { |
Hiroshi Shimamoto | 0cd418d | 2008-08-18 14:39:21 -0700 | [diff] [blame] | 741 | unsigned long flags; |
Paul E. McKenney | cd95851 | 2008-08-17 07:37:15 -0700 | [diff] [blame] | 742 | |
| 743 | spin_lock_irqsave(&rcp->lock, flags); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 744 | memset(rdp, 0, sizeof(*rdp)); |
Lai Jiangshan | 5127bed | 2008-07-06 17:23:59 +0800 | [diff] [blame] | 745 | rdp->nxttail[0] = rdp->nxttail[1] = rdp->nxttail[2] = &rdp->nxtlist; |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 746 | rdp->donetail = &rdp->donelist; |
| 747 | rdp->quiescbatch = rcp->completed; |
| 748 | rdp->qs_pending = 0; |
| 749 | rdp->cpu = cpu; |
| 750 | rdp->blimit = blimit; |
Paul E. McKenney | cd95851 | 2008-08-17 07:37:15 -0700 | [diff] [blame] | 751 | spin_unlock_irqrestore(&rcp->lock, flags); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 752 | } |
| 753 | |
| 754 | static void __cpuinit rcu_online_cpu(int cpu) |
| 755 | { |
| 756 | struct rcu_data *rdp = &per_cpu(rcu_data, cpu); |
| 757 | struct rcu_data *bh_rdp = &per_cpu(rcu_bh_data, cpu); |
| 758 | |
| 759 | rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp); |
| 760 | rcu_init_percpu_data(cpu, &rcu_bh_ctrlblk, bh_rdp); |
Carlos R. Mafra | 962cf36 | 2008-05-15 11:15:37 -0300 | [diff] [blame] | 761 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 762 | } |
| 763 | |
| 764 | static int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
| 765 | unsigned long action, void *hcpu) |
| 766 | { |
| 767 | long cpu = (long)hcpu; |
| 768 | |
| 769 | switch (action) { |
| 770 | case CPU_UP_PREPARE: |
| 771 | case CPU_UP_PREPARE_FROZEN: |
| 772 | rcu_online_cpu(cpu); |
| 773 | break; |
| 774 | case CPU_DEAD: |
| 775 | case CPU_DEAD_FROZEN: |
| 776 | rcu_offline_cpu(cpu); |
| 777 | break; |
| 778 | default: |
| 779 | break; |
| 780 | } |
| 781 | return NOTIFY_OK; |
| 782 | } |
| 783 | |
| 784 | static struct notifier_block __cpuinitdata rcu_nb = { |
| 785 | .notifier_call = rcu_cpu_notify, |
| 786 | }; |
| 787 | |
| 788 | /* |
| 789 | * Initializes rcu mechanism. Assumed to be called early. |
| 790 | * That is before local timer(SMP) or jiffie timer (uniproc) is setup. |
| 791 | * Note that rcu_qsctr and friends are implicitly |
| 792 | * initialized due to the choice of ``0'' for RCU_CTR_INVALID. |
| 793 | */ |
| 794 | void __init __rcu_init(void) |
| 795 | { |
Paul E. McKenney | 2133b5d | 2008-10-02 16:06:39 -0700 | [diff] [blame] | 796 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
| 797 | printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n"); |
| 798 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 799 | rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, |
| 800 | (void *)(long)smp_processor_id()); |
| 801 | /* Register notifier for non-boot CPUs */ |
| 802 | register_cpu_notifier(&rcu_nb); |
| 803 | } |
| 804 | |
| 805 | module_param(blimit, int, 0); |
| 806 | module_param(qhimark, int, 0); |
| 807 | module_param(qlowmark, int, 0); |