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 <laijs@cn.fujitsu.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Paul E. McKenney
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deb7a41815
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7b27d5475f
@ -25,6 +25,7 @@
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*/
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#include <linux/delay.h>
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#include <linux/stop_machine.h>
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/*
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* Check the RCU kernel configuration parameters and print informative
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@ -1014,6 +1015,76 @@ static void __init __rcu_init_preempt(void)
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#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
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#ifndef CONFIG_SMP
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void synchronize_sched_expedited(void)
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{
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cond_resched();
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}
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EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
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#else /* #ifndef CONFIG_SMP */
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static atomic_t synchronize_sched_expedited_count = ATOMIC_INIT(0);
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static int synchronize_sched_expedited_cpu_stop(void *data)
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{
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/*
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* There must be a full memory barrier on each affected CPU
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* between the time that try_stop_cpus() is called and the
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* time that it returns.
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*
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* In the current initial implementation of cpu_stop, the
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* above condition is already met when the control reaches
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* this point and the following smp_mb() is not strictly
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* necessary. Do smp_mb() anyway for documentation and
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* robustness against future implementation changes.
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*/
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smp_mb(); /* See above comment block. */
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return 0;
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}
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/*
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* Wait for an rcu-sched grace period to elapse, but use "big hammer"
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* approach to force grace period to end quickly. This consumes
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* significant time on all CPUs, and is thus not recommended for
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* any sort of common-case code.
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*
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* Note that it is illegal to call this function while holding any
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* lock that is acquired by a CPU-hotplug notifier. Failing to
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* observe this restriction will result in deadlock.
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*/
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void synchronize_sched_expedited(void)
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{
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int snap, trycount = 0;
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smp_mb(); /* ensure prior mod happens before capturing snap. */
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snap = atomic_read(&synchronize_sched_expedited_count) + 1;
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get_online_cpus();
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while (try_stop_cpus(cpu_online_mask,
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synchronize_sched_expedited_cpu_stop,
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NULL) == -EAGAIN) {
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put_online_cpus();
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if (trycount++ < 10)
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udelay(trycount * num_online_cpus());
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else {
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synchronize_sched();
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return;
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}
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if (atomic_read(&synchronize_sched_expedited_count) - snap > 0) {
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smp_mb(); /* ensure test happens before caller kfree */
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return;
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}
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get_online_cpus();
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}
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atomic_inc(&synchronize_sched_expedited_count);
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smp_mb__after_atomic_inc(); /* ensure post-GP actions seen after GP. */
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put_online_cpus();
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}
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EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
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#endif /* #else #ifndef CONFIG_SMP */
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#if !defined(CONFIG_RCU_FAST_NO_HZ)
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/*
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