| /* |
| * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition. |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write to the Free Software |
| * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| * |
| * Copyright IBM Corporation, 2008 |
| * |
| * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
| * |
| * For detailed explanation of Read-Copy Update mechanism see - |
| * Documentation/RCU |
| */ |
| #include <linux/completion.h> |
| #include <linux/interrupt.h> |
| #include <linux/notifier.h> |
| #include <linux/rcupdate.h> |
| #include <linux/kernel.h> |
| #include <linux/export.h> |
| #include <linux/mutex.h> |
| #include <linux/sched.h> |
| #include <linux/types.h> |
| #include <linux/init.h> |
| #include <linux/time.h> |
| #include <linux/cpu.h> |
| #include <linux/prefetch.h> |
| #include <linux/ftrace_event.h> |
| |
| #ifdef CONFIG_RCU_TRACE |
| #include <trace/events/rcu.h> |
| #endif /* #else #ifdef CONFIG_RCU_TRACE */ |
| |
| #include "rcu.h" |
| |
| /* Forward declarations for tiny_plugin.h. */ |
| struct rcu_ctrlblk; |
| static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp); |
| static void rcu_process_callbacks(struct softirq_action *unused); |
| static void __call_rcu(struct rcu_head *head, |
| void (*func)(struct rcu_head *rcu), |
| struct rcu_ctrlblk *rcp); |
| |
| static long long rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; |
| |
| #include "tiny_plugin.h" |
| |
| /* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */ |
| static void rcu_idle_enter_common(long long newval) |
| { |
| if (newval) { |
| RCU_TRACE(trace_rcu_dyntick(TPS("--="), |
| rcu_dynticks_nesting, newval)); |
| rcu_dynticks_nesting = newval; |
| return; |
| } |
| RCU_TRACE(trace_rcu_dyntick(TPS("Start"), |
| rcu_dynticks_nesting, newval)); |
| if (!is_idle_task(current)) { |
| struct task_struct *idle __maybe_unused = idle_task(smp_processor_id()); |
| |
| RCU_TRACE(trace_rcu_dyntick(TPS("Entry error: not idle task"), |
| rcu_dynticks_nesting, newval)); |
| ftrace_dump(DUMP_ALL); |
| WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
| current->pid, current->comm, |
| idle->pid, idle->comm); /* must be idle task! */ |
| } |
| rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */ |
| barrier(); |
| rcu_dynticks_nesting = newval; |
| } |
| |
| /* |
| * Enter idle, which is an extended quiescent state if we have fully |
| * entered that mode (i.e., if the new value of dynticks_nesting is zero). |
| */ |
| void rcu_idle_enter(void) |
| { |
| unsigned long flags; |
| long long newval; |
| |
| local_irq_save(flags); |
| WARN_ON_ONCE((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) == 0); |
| if ((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) == |
| DYNTICK_TASK_NEST_VALUE) |
| newval = 0; |
| else |
| newval = rcu_dynticks_nesting - DYNTICK_TASK_NEST_VALUE; |
| rcu_idle_enter_common(newval); |
| local_irq_restore(flags); |
| } |
| EXPORT_SYMBOL_GPL(rcu_idle_enter); |
| |
| /* |
| * Exit an interrupt handler towards idle. |
| */ |
| void rcu_irq_exit(void) |
| { |
| unsigned long flags; |
| long long newval; |
| |
| local_irq_save(flags); |
| newval = rcu_dynticks_nesting - 1; |
| WARN_ON_ONCE(newval < 0); |
| rcu_idle_enter_common(newval); |
| local_irq_restore(flags); |
| } |
| EXPORT_SYMBOL_GPL(rcu_irq_exit); |
| |
| /* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcutree.c. */ |
| static void rcu_idle_exit_common(long long oldval) |
| { |
| if (oldval) { |
| RCU_TRACE(trace_rcu_dyntick(TPS("++="), |
| oldval, rcu_dynticks_nesting)); |
| return; |
| } |
| RCU_TRACE(trace_rcu_dyntick(TPS("End"), oldval, rcu_dynticks_nesting)); |
| if (!is_idle_task(current)) { |
| struct task_struct *idle __maybe_unused = idle_task(smp_processor_id()); |
| |
| RCU_TRACE(trace_rcu_dyntick(TPS("Exit error: not idle task"), |
| oldval, rcu_dynticks_nesting)); |
| ftrace_dump(DUMP_ALL); |
| WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s", |
| current->pid, current->comm, |
| idle->pid, idle->comm); /* must be idle task! */ |
| } |
| } |
| |
| /* |
| * Exit idle, so that we are no longer in an extended quiescent state. |
| */ |
| void rcu_idle_exit(void) |
| { |
| unsigned long flags; |
| long long oldval; |
| |
| local_irq_save(flags); |
| oldval = rcu_dynticks_nesting; |
| WARN_ON_ONCE(rcu_dynticks_nesting < 0); |
| if (rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) |
| rcu_dynticks_nesting += DYNTICK_TASK_NEST_VALUE; |
| else |
| rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; |
| rcu_idle_exit_common(oldval); |
| local_irq_restore(flags); |
| } |
| EXPORT_SYMBOL_GPL(rcu_idle_exit); |
| |
| /* |
| * Enter an interrupt handler, moving away from idle. |
| */ |
| void rcu_irq_enter(void) |
| { |
| unsigned long flags; |
| long long oldval; |
| |
| local_irq_save(flags); |
| oldval = rcu_dynticks_nesting; |
| rcu_dynticks_nesting++; |
| WARN_ON_ONCE(rcu_dynticks_nesting == 0); |
| rcu_idle_exit_common(oldval); |
| local_irq_restore(flags); |
| } |
| EXPORT_SYMBOL_GPL(rcu_irq_enter); |
| |
| #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) |
| |
| /* |
| * Test whether RCU thinks that the current CPU is idle. |
| */ |
| bool __rcu_is_watching(void) |
| { |
| return rcu_dynticks_nesting; |
| } |
| EXPORT_SYMBOL(__rcu_is_watching); |
| |
| #endif /* defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */ |
| |
| /* |
| * Test whether the current CPU was interrupted from idle. Nested |
| * interrupts don't count, we must be running at the first interrupt |
| * level. |
| */ |
| static int rcu_is_cpu_rrupt_from_idle(void) |
| { |
| return rcu_dynticks_nesting <= 1; |
| } |
| |
| /* |
| * Helper function for rcu_sched_qs() and rcu_bh_qs(). |
| * Also irqs are disabled to avoid confusion due to interrupt handlers |
| * invoking call_rcu(). |
| */ |
| static int rcu_qsctr_help(struct rcu_ctrlblk *rcp) |
| { |
| RCU_TRACE(reset_cpu_stall_ticks(rcp)); |
| if (rcp->rcucblist != NULL && |
| rcp->donetail != rcp->curtail) { |
| rcp->donetail = rcp->curtail; |
| return 1; |
| } |
| |
| return 0; |
| } |
| |
| /* |
| * Record an rcu quiescent state. And an rcu_bh quiescent state while we |
| * are at it, given that any rcu quiescent state is also an rcu_bh |
| * quiescent state. Use "+" instead of "||" to defeat short circuiting. |
| */ |
| void rcu_sched_qs(int cpu) |
| { |
| unsigned long flags; |
| |
| local_irq_save(flags); |
| if (rcu_qsctr_help(&rcu_sched_ctrlblk) + |
| rcu_qsctr_help(&rcu_bh_ctrlblk)) |
| raise_softirq(RCU_SOFTIRQ); |
| local_irq_restore(flags); |
| } |
| |
| /* |
| * Record an rcu_bh quiescent state. |
| */ |
| void rcu_bh_qs(int cpu) |
| { |
| unsigned long flags; |
| |
| local_irq_save(flags); |
| if (rcu_qsctr_help(&rcu_bh_ctrlblk)) |
| raise_softirq(RCU_SOFTIRQ); |
| local_irq_restore(flags); |
| } |
| |
| /* |
| * Check to see if the scheduling-clock interrupt came from an extended |
| * quiescent state, and, if so, tell RCU about it. This function must |
| * be called from hardirq context. It is normally called from the |
| * scheduling-clock interrupt. |
| */ |
| void rcu_check_callbacks(int cpu, int user) |
| { |
| RCU_TRACE(check_cpu_stalls()); |
| if (user || rcu_is_cpu_rrupt_from_idle()) |
| rcu_sched_qs(cpu); |
| else if (!in_softirq()) |
| rcu_bh_qs(cpu); |
| } |
| |
| /* |
| * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure |
| * whose grace period has elapsed. |
| */ |
| static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) |
| { |
| const char *rn = NULL; |
| struct rcu_head *next, *list; |
| unsigned long flags; |
| RCU_TRACE(int cb_count = 0); |
| |
| /* If no RCU callbacks ready to invoke, just return. */ |
| if (&rcp->rcucblist == rcp->donetail) { |
| RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, 0, -1)); |
| RCU_TRACE(trace_rcu_batch_end(rcp->name, 0, |
| !!ACCESS_ONCE(rcp->rcucblist), |
| need_resched(), |
| is_idle_task(current), |
| false)); |
| return; |
| } |
| |
| /* Move the ready-to-invoke callbacks to a local list. */ |
| local_irq_save(flags); |
| RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, rcp->qlen, -1)); |
| list = rcp->rcucblist; |
| rcp->rcucblist = *rcp->donetail; |
| *rcp->donetail = NULL; |
| if (rcp->curtail == rcp->donetail) |
| rcp->curtail = &rcp->rcucblist; |
| rcp->donetail = &rcp->rcucblist; |
| local_irq_restore(flags); |
| |
| /* Invoke the callbacks on the local list. */ |
| RCU_TRACE(rn = rcp->name); |
| while (list) { |
| next = list->next; |
| prefetch(next); |
| debug_rcu_head_unqueue(list); |
| local_bh_disable(); |
| __rcu_reclaim(rn, list); |
| local_bh_enable(); |
| list = next; |
| RCU_TRACE(cb_count++); |
| } |
| RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count)); |
| RCU_TRACE(trace_rcu_batch_end(rcp->name, |
| cb_count, 0, need_resched(), |
| is_idle_task(current), |
| false)); |
| } |
| |
| static void rcu_process_callbacks(struct softirq_action *unused) |
| { |
| __rcu_process_callbacks(&rcu_sched_ctrlblk); |
| __rcu_process_callbacks(&rcu_bh_ctrlblk); |
| } |
| |
| /* |
| * Wait for a grace period to elapse. But it is illegal to invoke |
| * synchronize_sched() from within an RCU read-side critical section. |
| * Therefore, any legal call to synchronize_sched() is a quiescent |
| * state, and so on a UP system, synchronize_sched() need do nothing. |
| * Ditto for synchronize_rcu_bh(). (But Lai Jiangshan points out the |
| * benefits of doing might_sleep() to reduce latency.) |
| * |
| * Cool, huh? (Due to Josh Triplett.) |
| * |
| * But we want to make this a static inline later. The cond_resched() |
| * currently makes this problematic. |
| */ |
| void synchronize_sched(void) |
| { |
| rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) && |
| !lock_is_held(&rcu_lock_map) && |
| !lock_is_held(&rcu_sched_lock_map), |
| "Illegal synchronize_sched() in RCU read-side critical section"); |
| cond_resched(); |
| } |
| EXPORT_SYMBOL_GPL(synchronize_sched); |
| |
| /* |
| * Helper function for call_rcu() and call_rcu_bh(). |
| */ |
| static void __call_rcu(struct rcu_head *head, |
| void (*func)(struct rcu_head *rcu), |
| struct rcu_ctrlblk *rcp) |
| { |
| unsigned long flags; |
| |
| debug_rcu_head_queue(head); |
| head->func = func; |
| head->next = NULL; |
| |
| local_irq_save(flags); |
| *rcp->curtail = head; |
| rcp->curtail = &head->next; |
| RCU_TRACE(rcp->qlen++); |
| local_irq_restore(flags); |
| } |
| |
| /* |
| * Post an RCU callback to be invoked after the end of an RCU-sched grace |
| * period. But since we have but one CPU, that would be after any |
| * quiescent state. |
| */ |
| void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
| { |
| __call_rcu(head, func, &rcu_sched_ctrlblk); |
| } |
| EXPORT_SYMBOL_GPL(call_rcu_sched); |
| |
| /* |
| * Post an RCU bottom-half callback to be invoked after any subsequent |
| * quiescent state. |
| */ |
| void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
| { |
| __call_rcu(head, func, &rcu_bh_ctrlblk); |
| } |
| EXPORT_SYMBOL_GPL(call_rcu_bh); |
| |
| void rcu_init(void) |
| { |
| open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
| } |