Commit 05ef9e9e authored Aug 15, 2019 by Joel Fernandes (Google) Committed by Paul E. McKenney Oct 30, 2019

rcu: Ensure that ->rcu_urgent_qs is set before resched IPI



The RCU-specific resched_cpu() function sends a resched IPI to the
specified CPU, which can be used to force the tick on for a given
nohz_full CPU.  This is needed when this nohz_full CPU is looping in the
kernel while blocking the current grace period.  However, for the tick
to actually be forced on in all cases, that CPU's rcu_data structure's
->rcu_urgent_qs flag must be set beforehand.  This commit therefore
causes rcu_implicit_dynticks_qs() to set this flag prior to invoking
resched_cpu() on a holdout nohz_full CPU.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

parent 5a644662

kernel/rcu/tree.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -1073,6 +1073,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
		if (tick_nohz_full_cpu(rdp->cpu) &&
		time_after(jiffies,
		READ_ONCE(rdp->last_fqs_resched) + jtsq * 3)) {
		WRITE_ONCE(*ruqp, true);
		resched_cpu(rdp->cpu);
		WRITE_ONCE(rdp->last_fqs_resched, jiffies);
		}

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