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rcu: Avoid resched_cpu() when rescheduling the current CPU

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The resched_cpu() interface is quite handy, but it does acquire the
specified CPU's runqueue lock, which does not come for free.  This
commit therefore substitutes the following when directing resched_cpu()
at the current CPU:

	set_tsk_need_resched(current);
	set_preempt_need_resched();

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
This commit is contained in:
Paul E. McKenney
2018-07-26 13:44:00 -07:00
parent d3052109c0
commit fced9c8cfe
3 changed files with 21 additions and 13 deletions
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6
kernel/rcu/tree_plugin.h
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@@ -791,8 +791,10 @@ static void rcu_flavor_check_callbacks(int user)
if (t->rcu_read_lock_nesting > 0 ||
(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK))) {
/* No QS, force context switch if deferred. */
if (rcu_preempt_need_deferred_qs(t))
resched_cpu(smp_processor_id());
if (rcu_preempt_need_deferred_qs(t)) {
set_tsk_need_resched(t);
set_preempt_need_resched();
}
} else if (rcu_preempt_need_deferred_qs(t)) {
rcu_preempt_deferred_qs(t); /* Report deferred QS. */
return;