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kernel/rcutiny.c
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/* * 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 - |
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* Documentation/RCU |
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*/ |
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#include <linux/completion.h> #include <linux/interrupt.h> |
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#include <linux/notifier.h> |
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#include <linux/rcupdate.h> #include <linux/kernel.h> |
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#include <linux/export.h> |
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#include <linux/mutex.h> |
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#include <linux/sched.h> #include <linux/types.h> #include <linux/init.h> |
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#include <linux/time.h> |
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#include <linux/cpu.h> |
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#include <linux/prefetch.h> |
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#ifdef CONFIG_RCU_TRACE |
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#include <trace/events/rcu.h> |
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#endif /* #else #ifdef CONFIG_RCU_TRACE */ #include "rcu.h" |
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/* Forward declarations for rcutiny_plugin.h. */ |
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struct rcu_ctrlblk; |
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static void invoke_rcu_callbacks(void); static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp); static void rcu_process_callbacks(struct softirq_action *unused); |
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static void __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), struct rcu_ctrlblk *rcp); #include "rcutiny_plugin.h" |
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#ifdef CONFIG_NO_HZ static long rcu_dynticks_nesting = 1; /* * Enter dynticks-idle mode, 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_enter_nohz(void) { if (--rcu_dynticks_nesting == 0) rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */ } /* * Exit dynticks-idle mode, so that we are no longer in an extended * quiescent state. */ void rcu_exit_nohz(void) { rcu_dynticks_nesting++; } #endif /* #ifdef CONFIG_NO_HZ */ /* |
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* Helper function for rcu_sched_qs() and rcu_bh_qs(). * Also irqs are disabled to avoid confusion due to interrupt handlers |
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* invoking call_rcu(). |
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*/ static int rcu_qsctr_help(struct rcu_ctrlblk *rcp) { |
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if (rcp->rcucblist != NULL && rcp->donetail != rcp->curtail) { rcp->donetail = rcp->curtail; |
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return 1; } |
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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) { |
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unsigned long flags; local_irq_save(flags); |
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if (rcu_qsctr_help(&rcu_sched_ctrlblk) + rcu_qsctr_help(&rcu_bh_ctrlblk)) |
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invoke_rcu_callbacks(); |
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local_irq_restore(flags); |
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} /* * Record an rcu_bh quiescent state. */ void rcu_bh_qs(int cpu) { |
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unsigned long flags; local_irq_save(flags); |
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if (rcu_qsctr_help(&rcu_bh_ctrlblk)) |
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invoke_rcu_callbacks(); |
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local_irq_restore(flags); |
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} /* * Check to see if the scheduling-clock interrupt came from an extended * quiescent state, and, if so, tell RCU about it. */ void rcu_check_callbacks(int cpu, int user) { if (user || (idle_cpu(cpu) && !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) rcu_sched_qs(cpu); else if (!in_softirq()) rcu_bh_qs(cpu); |
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rcu_preempt_check_callbacks(); |
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} /* |
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* Invoke the RCU callbacks on the specified rcu_ctrlkblk structure * whose grace period has elapsed. |
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*/ |
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static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) |
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{ |
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char *rn = NULL; |
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struct rcu_head *next, *list; |
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unsigned long flags; |
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RCU_TRACE(int cb_count = 0); |
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/* If no RCU callbacks ready to invoke, just return. */ |
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if (&rcp->rcucblist == rcp->donetail) { |
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RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, -1)); RCU_TRACE(trace_rcu_batch_end(rcp->name, 0)); |
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return; |
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} |
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/* Move the ready-to-invoke callbacks to a local list. */ local_irq_save(flags); |
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RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, -1)); |
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list = rcp->rcucblist; rcp->rcucblist = *rcp->donetail; *rcp->donetail = NULL; if (rcp->curtail == rcp->donetail) rcp->curtail = &rcp->rcucblist; |
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rcu_preempt_remove_callbacks(rcp); |
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rcp->donetail = &rcp->rcucblist; local_irq_restore(flags); /* Invoke the callbacks on the local list. */ |
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RCU_TRACE(rn = rcp->name); |
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while (list) { next = list->next; prefetch(next); |
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debug_rcu_head_unqueue(list); |
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local_bh_disable(); |
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__rcu_reclaim(rn, list); |
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local_bh_enable(); |
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list = next; |
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RCU_TRACE(cb_count++); |
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} |
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RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count)); |
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RCU_TRACE(trace_rcu_batch_end(rcp->name, cb_count)); |
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} |
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static void rcu_process_callbacks(struct softirq_action *unused) |
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{ |
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__rcu_process_callbacks(&rcu_sched_ctrlblk); __rcu_process_callbacks(&rcu_bh_ctrlblk); rcu_preempt_process_callbacks(); |
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} /* |
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* 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.) * |
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* But we want to make this a static inline later. The cond_resched() * currently makes this problematic. |
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*/ void synchronize_sched(void) { cond_resched(); } EXPORT_SYMBOL_GPL(synchronize_sched); |
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/* * 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; |
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debug_rcu_head_queue(head); |
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head->func = func; head->next = NULL; |
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local_irq_save(flags); *rcp->curtail = head; rcp->curtail = &head->next; |
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RCU_TRACE(rcp->qlen++); |
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local_irq_restore(flags); } /* |
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* Post an RCU callback to be invoked after the end of an RCU-sched grace |
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* period. But since we have but one CPU, that would be after any * quiescent state. */ |
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void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
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{ |
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__call_rcu(head, func, &rcu_sched_ctrlblk); |
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} |
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EXPORT_SYMBOL_GPL(call_rcu_sched); |
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/* * Post an RCU bottom-half callback to be invoked after any subsequent * quiescent state. */ |
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void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
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{ __call_rcu(head, func, &rcu_bh_ctrlblk); } EXPORT_SYMBOL_GPL(call_rcu_bh); |