From: Daniel Jordan <daniel.m.jordan@oracle.com>
To: Tejun Heo <tj@kernel.org>, Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Hillf Danton <hdanton@sina.com>,
Daniel Jordan <daniel.m.jordan@oracle.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH] workqueue: don't use wq_select_unbound_cpu() for bound works
Date: Fri, 24 Jan 2020 20:14:45 -0500 [thread overview]
Message-ID: <20200125011445.983252-1-daniel.m.jordan@oracle.com> (raw)
From: Hillf Danton <hdanton@sina.com>
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: ef557180447f ("workqueue: schedule WORK_CPU_UNBOUND work on wq_unbound_cpumask CPUs")
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
---
kernel/workqueue.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index cfc923558e04..6978892b0d8a 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1411,14 +1411,16 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
return;
rcu_read_lock();
retry:
- 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
+ if (wq->flags & WQ_UNBOUND) {
+ if (req_cpu == WORK_CPU_UNBOUND)
+ cpu = wq_select_unbound_cpu(raw_smp_processor_id());
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
--
2.24.1
next reply other threads:[~2020-01-25 1:15 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-25 1:14 Daniel Jordan [this message]
2020-02-12 21:08 ` [PATCH] workqueue: don't use wq_select_unbound_cpu() for bound works Tejun Heo
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