From: Lai Jiangshan <jiangshanlai@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>, Qian Cai <cai@redhat.com>,
Vincent Donnefort <vincent.donnefort@arm.com>,
Dexuan Cui <decui@microsoft.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Steven Rostedt <rostedt@goodmis.org>, Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH 3/4] workqueue: Tag bound workers with KTHREAD_IS_PER_CPU
Date: Sun, 17 Jan 2021 00:14:34 +0800 [thread overview]
Message-ID: <CAJhGHyBKexR+UmR2Hzf-OU9_9zfc0V6r=s2rS=N8sc+2VnN3mw@mail.gmail.com> (raw)
In-Reply-To: <YAMDUQ7JX2Fr8D+/@hirez.programming.kicks-ass.net>
On Sat, Jan 16, 2021 at 11:16 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Sat, Jan 16, 2021 at 10:45:04PM +0800, Lai Jiangshan wrote:
> > On Sat, Jan 16, 2021 at 8:45 PM Peter Zijlstra <peterz@infradead.org> wrote:
> > > It is also the exact sequence normal per-cpu threads (smpboot) use to
> > > preserve affinity.
> >
> > Other per-cpu threads normally do short-live works. wq's work can be
> > lengthy, cpu-intensive, heavy-lock-acquiring or even call
> > get_online_cpus() which might result in a deadlock with kthread_park().
>
> kthread_park() is called by the migration thread running the
> workqueue_online_cpu() callback.
>
> kthread_parkme() is called by the worker thread, after it completes a
> work and has no locks held from that context.
>
>
BP: AP: worker:
cpus_write_lock()
bringup_cpu() work_item_func()
bringup_wait_for_ap get_online_cpus()
kthread_park(worker)
next prev parent reply other threads:[~2021-01-16 17:13 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-12 14:43 [PATCH 0/4] sched: Fix hot-unplug regressions Peter Zijlstra
2021-01-12 14:43 ` [PATCH 2/4] kthread: Extract KTHREAD_IS_PER_CPU Peter Zijlstra
2021-01-12 14:43 ` [PATCH 3/4] workqueue: Tag bound workers with KTHREAD_IS_PER_CPU Peter Zijlstra
2021-01-12 16:36 ` Lai Jiangshan
2021-01-13 11:43 ` Peter Zijlstra
2021-01-12 17:57 ` Valentin Schneider
2021-01-13 13:28 ` Lai Jiangshan
2021-01-13 14:16 ` Valentin Schneider
2021-01-13 17:52 ` Paul E. McKenney
2021-01-13 18:43 ` Valentin Schneider
2021-01-13 18:59 ` Paul E. McKenney
2021-01-14 13:12 ` Peter Zijlstra
2021-01-14 13:21 ` Valentin Schneider
2021-01-14 15:34 ` Peter Zijlstra
2021-01-16 6:27 ` Lai Jiangshan
2021-01-16 12:45 ` Peter Zijlstra
2021-01-16 14:45 ` Lai Jiangshan
2021-01-16 15:16 ` Peter Zijlstra
2021-01-16 16:14 ` Lai Jiangshan [this message]
2021-01-16 18:46 ` Peter Zijlstra
2021-01-17 9:54 ` Peter Zijlstra
2021-01-16 15:13 ` Peter Zijlstra
2021-01-12 14:43 ` [PATCH 4/4] sched: Fix CPU hotplug / tighten is_per_cpu_kthread() Peter Zijlstra
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