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Commit a979047c authored by Kyle Yan's avatar Kyle Yan
Browse files

Revert "sched: Remove synchronize rcu/sched calls from _cpu_down" 



This reverts commit c9e8afb8.

Removing the synchronization of rcu/sched calls from _cpu_down introduces
a race where tasks may get queued on an inactive CPU and unthrottling
cfs_rqs.

Change-Id: I3a24314a403fc7352f506cda0016963621c79f6a
Signed-off-by: default avatarKyle Yan <kyan@codeaurora.org>
parent 123357f5

kernel/sched/core.c

+14 −0
Original line number Diff line number Diff line
@@ -8052,6 +8052,20 @@ int sched_cpu_deactivate(unsigned int cpu) 
	int ret;



	set_cpu_active(cpu, false);

	/*

	 * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU

	 * users of this state to go away such that all new such users will

	 * observe it.

	 *

	 * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might

	 * not imply sync_sched(), so wait for both.

	 *

	 * Do sync before park smpboot threads to take care the rcu boost case.

	 */

	if (IS_ENABLED(CONFIG_PREEMPT))

		synchronize_rcu_mult(call_rcu, call_rcu_sched);

	else

		synchronize_rcu();



	if (!sched_smp_initialized)

		return 0;