From 7b27d5475f86186914e54e4a6bb994e9a985337b Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Thu, 21 Oct 2010 11:29:05 +0800 Subject: rcu,cleanup: move synchronize_sched_expedited() out of sched.c The first version of synchronize_sched_expedited() used the migration code in the scheduler, and was therefore implemented in kernel/sched.c. However, the more recent version of this code no longer uses the migration code, so this commit moves it to the main RCU source files. Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney --- kernel/rcutree_plugin.h | 71 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 71 insertions(+) (limited to 'kernel/rcutree_plugin.h') diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 71a4147473f9..21df7f3e7273 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -25,6 +25,7 @@ */ #include +#include /* * Check the RCU kernel configuration parameters and print informative @@ -1014,6 +1015,76 @@ static void __init __rcu_init_preempt(void) #endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ +#ifndef CONFIG_SMP + +void synchronize_sched_expedited(void) +{ + cond_resched(); +} +EXPORT_SYMBOL_GPL(synchronize_sched_expedited); + +#else /* #ifndef CONFIG_SMP */ + +static atomic_t synchronize_sched_expedited_count = ATOMIC_INIT(0); + +static int synchronize_sched_expedited_cpu_stop(void *data) +{ + /* + * There must be a full memory barrier on each affected CPU + * between the time that try_stop_cpus() is called and the + * time that it returns. + * + * In the current initial implementation of cpu_stop, the + * above condition is already met when the control reaches + * this point and the following smp_mb() is not strictly + * necessary. Do smp_mb() anyway for documentation and + * robustness against future implementation changes. + */ + smp_mb(); /* See above comment block. */ + return 0; +} + +/* + * Wait for an rcu-sched grace period to elapse, but use "big hammer" + * approach to force grace period to end quickly. This consumes + * significant time on all CPUs, and is thus not recommended for + * any sort of common-case code. + * + * Note that it is illegal to call this function while holding any + * lock that is acquired by a CPU-hotplug notifier. Failing to + * observe this restriction will result in deadlock. + */ +void synchronize_sched_expedited(void) +{ + int snap, trycount = 0; + + smp_mb(); /* ensure prior mod happens before capturing snap. */ + snap = atomic_read(&synchronize_sched_expedited_count) + 1; + get_online_cpus(); + while (try_stop_cpus(cpu_online_mask, + synchronize_sched_expedited_cpu_stop, + NULL) == -EAGAIN) { + put_online_cpus(); + if (trycount++ < 10) + udelay(trycount * num_online_cpus()); + else { + synchronize_sched(); + return; + } + if (atomic_read(&synchronize_sched_expedited_count) - snap > 0) { + smp_mb(); /* ensure test happens before caller kfree */ + return; + } + get_online_cpus(); + } + atomic_inc(&synchronize_sched_expedited_count); + smp_mb__after_atomic_inc(); /* ensure post-GP actions seen after GP. */ + put_online_cpus(); +} +EXPORT_SYMBOL_GPL(synchronize_sched_expedited); + +#endif /* #else #ifndef CONFIG_SMP */ + #if !defined(CONFIG_RCU_FAST_NO_HZ) /* -- cgit v1.2.3