Commit 3ba4d0e0 authored Nov 12, 2014 by Paul E. McKenney

rcu: Note quiescent state when CPU goes offline

The rcu_cleanup_dead_cpu() function (called after a CPU has gone
completely offline) has not reported a quiescent state because there
was probably at least one synchronize_rcu() between the time the CPU
went offline and the CPU_DEAD notifier, and this would have detected
the CPU's offline state via quiescent-state forcing. However, the plan
is for CPUs to take themselves offline, at which point it makes sense
for them to report their own quiescent state. This commit makes this
change in preparation for the new CPU-hotplug setup.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

parent 5d0b0249

kernel/rcu/tree.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2297,7 +2297,7 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
		rnp->qsmaskinit &= ~rdp->grpmask;
		if (rnp->qsmaskinit == 0 && !rcu_preempt_has_tasks(rnp))
		rcu_cleanup_dead_rnp(rnp);
		raw_spin_unlock_irqrestore(&rnp->lock, flags);
		rcu_report_qs_rnp(rdp->grpmask, rsp, rnp, flags); /* Rlses rnp->lock. */
		WARN_ONCE(rdp->qlen != 0 \|\| rdp->nxtlist != NULL,
		"rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n",
		cpu, rdp->qlen, rdp->nxtlist);

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