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author | root <root@artemis.panaceas.org> | 2015-12-25 04:40:36 +0000 |
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committer | root <root@artemis.panaceas.org> | 2015-12-25 04:40:36 +0000 |
commit | 849369d6c66d3054688672f97d31fceb8e8230fb (patch) | |
tree | 6135abc790ca67dedbe07c39806591e70eda81ce /kernel/rcutiny.c | |
download | linux-3.0.35-kobo-849369d6c66d3054688672f97d31fceb8e8230fb.tar.gz linux-3.0.35-kobo-849369d6c66d3054688672f97d31fceb8e8230fb.tar.bz2 linux-3.0.35-kobo-849369d6c66d3054688672f97d31fceb8e8230fb.zip |
initial_commit
Diffstat (limited to 'kernel/rcutiny.c')
-rw-r--r-- | kernel/rcutiny.c | 324 |
1 files changed, 324 insertions, 0 deletions
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c new file mode 100644 index 00000000..7bbac7d0 --- /dev/null +++ b/kernel/rcutiny.c @@ -0,0 +1,324 @@ +/* + * 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/moduleparam.h> +#include <linux/completion.h> +#include <linux/interrupt.h> +#include <linux/notifier.h> +#include <linux/rcupdate.h> +#include <linux/kernel.h> +#include <linux/module.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> + +/* Controls for rcu_kthread() kthread, replacing RCU_SOFTIRQ used previously. */ +static struct task_struct *rcu_kthread_task; +static DECLARE_WAIT_QUEUE_HEAD(rcu_kthread_wq); +static unsigned long have_rcu_kthread_work; + +/* Forward declarations for rcutiny_plugin.h. */ +struct rcu_ctrlblk; +static void invoke_rcu_kthread(void); +static void rcu_process_callbacks(struct rcu_ctrlblk *rcp); +static int rcu_kthread(void *arg); +static void __call_rcu(struct rcu_head *head, + void (*func)(struct rcu_head *rcu), + struct rcu_ctrlblk *rcp); + +#include "rcutiny_plugin.h" + +#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 */ + +/* + * 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) +{ + if (rcp->rcucblist != NULL && + rcp->donetail != rcp->curtail) { + rcp->donetail = rcp->curtail; + return 1; + } + + return 0; +} + +/* + * Wake up rcu_kthread() to process callbacks now eligible for invocation + * or to boost readers. + */ +static void invoke_rcu_kthread(void) +{ + have_rcu_kthread_work = 1; + wake_up(&rcu_kthread_wq); +} + +/* + * 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)) + invoke_rcu_kthread(); + 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)) + invoke_rcu_kthread(); + 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. + */ +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); + rcu_preempt_check_callbacks(); +} + +/* + * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure + * whose grace period has elapsed. + */ +static void rcu_process_callbacks(struct rcu_ctrlblk *rcp) +{ + 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) + return; + + /* Move the ready-to-invoke callbacks to a local list. */ + local_irq_save(flags); + list = rcp->rcucblist; + rcp->rcucblist = *rcp->donetail; + *rcp->donetail = NULL; + if (rcp->curtail == rcp->donetail) + rcp->curtail = &rcp->rcucblist; + rcu_preempt_remove_callbacks(rcp); + rcp->donetail = &rcp->rcucblist; + local_irq_restore(flags); + + /* Invoke the callbacks on the local list. */ + while (list) { + next = list->next; + prefetch(next); + debug_rcu_head_unqueue(list); + local_bh_disable(); + __rcu_reclaim(list); + local_bh_enable(); + list = next; + RCU_TRACE(cb_count++); + } + RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count)); +} + +/* + * This kthread invokes RCU callbacks whose grace periods have + * elapsed. It is awakened as needed, and takes the place of the + * RCU_SOFTIRQ that was used previously for this purpose. + * This is a kthread, but it is never stopped, at least not until + * the system goes down. + */ +static int rcu_kthread(void *arg) +{ + unsigned long work; + unsigned long morework; + unsigned long flags; + + for (;;) { + wait_event_interruptible(rcu_kthread_wq, + have_rcu_kthread_work != 0); + morework = rcu_boost(); + local_irq_save(flags); + work = have_rcu_kthread_work; + have_rcu_kthread_work = morework; + local_irq_restore(flags); + if (work) { + rcu_process_callbacks(&rcu_sched_ctrlblk); + rcu_process_callbacks(&rcu_bh_ctrlblk); + rcu_preempt_process_callbacks(); + } + schedule_timeout_interruptible(1); /* Leave CPU for others. */ + } + + return 0; /* Not reached, but needed to shut gcc up. */ +} + +/* + * 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) +{ + 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_barrier_bh(void) +{ + struct rcu_synchronize rcu; + + init_rcu_head_on_stack(&rcu.head); + init_completion(&rcu.completion); + /* Will wake me after RCU finished. */ + call_rcu_bh(&rcu.head, wakeme_after_rcu); + /* Wait for it. */ + wait_for_completion(&rcu.completion); + destroy_rcu_head_on_stack(&rcu.head); +} +EXPORT_SYMBOL_GPL(rcu_barrier_bh); + +void rcu_barrier_sched(void) +{ + struct rcu_synchronize rcu; + + init_rcu_head_on_stack(&rcu.head); + init_completion(&rcu.completion); + /* Will wake me after RCU finished. */ + call_rcu_sched(&rcu.head, wakeme_after_rcu); + /* Wait for it. */ + wait_for_completion(&rcu.completion); + destroy_rcu_head_on_stack(&rcu.head); +} +EXPORT_SYMBOL_GPL(rcu_barrier_sched); + +/* + * Spawn the kthread that invokes RCU callbacks. + */ +static int __init rcu_spawn_kthreads(void) +{ + struct sched_param sp; + + rcu_kthread_task = kthread_run(rcu_kthread, NULL, "rcu_kthread"); + sp.sched_priority = RCU_BOOST_PRIO; + sched_setscheduler_nocheck(rcu_kthread_task, SCHED_FIFO, &sp); + return 0; +} +early_initcall(rcu_spawn_kthreads); |