Commit aa202f1f authored Jan 24, 2020 by Hillf Danton Committed by Tejun Heo Mar 10, 2020

workqueue: don't use wq_select_unbound_cpu() for bound works



wq_select_unbound_cpu() is designed for unbound workqueues only, but
it's wrongly called when using a bound workqueue too.

Fixing this ensures work queued to a bound workqueue with
cpu=WORK_CPU_UNBOUND always runs on the local CPU.

Before, that would happen only if wq_unbound_cpumask happened to include
it (likely almost always the case), or was empty, or we got lucky with
forced round-robin placement.  So restricting
/sys/devices/virtual/workqueue/cpumask to a small subset of a machine's
CPUs would cause some bound work items to run unexpectedly there.

Fixes: ef557180 ("workqueue: schedule WORK_CPU_UNBOUND work on wq_unbound_cpumask CPUs")
Cc: stable@vger.kernel.org # v4.5+
Signed-off-by: Hillf Danton <hdanton@sina.com>
[dj: massage changelog]
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Tejun Heo <tj@kernel.org>

parent dbb92f88

kernel/workqueue.c

+8 −6

Original line number	Diff line number	Diff line
		@@ -1411,14 +1411,16 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
		return;
		rcu_read_lock();
		retry:
		/* pwq which will be used unless @work is executing elsewhere */
		if (wq->flags & WQ_UNBOUND) {
		if (req_cpu == WORK_CPU_UNBOUND)
		cpu = wq_select_unbound_cpu(raw_smp_processor_id());

		/* pwq which will be used unless @work is executing elsewhere */
		if (!(wq->flags & WQ_UNBOUND))
		pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
		else
		pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
		} else {
		if (req_cpu == WORK_CPU_UNBOUND)
		cpu = raw_smp_processor_id();
		pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
		}

		/*
		* If @work was previously on a different pool, it might still be

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