From: Lai Jiangshan <jiangshanlai@gmail.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: kernel test robot <lkp@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>, LKP <lkp@lists.01.org>,
Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH] workqueue: Don't double assign worker->sleeping
Date: Thu, 2 Apr 2020 08:07:35 +0800 [thread overview]
Message-ID: <CAJhGHyBmcY75Rhc7UFyK7Ozho+aqOcX2EaxePhZFu9rt0w3-mA@mail.gmail.com> (raw)
In-Reply-To: <20200401130346.e7cdsqgxppa6ohje@linutronix.de>
On Wed, Apr 1, 2020 at 9:03 PM Sebastian Andrzej Siewior
<bigeasy@linutronix.de> wrote:
>
> On 2020-04-01 11:44:06 [+0800], Lai Jiangshan wrote:
> > On Wed, Apr 1, 2020 at 11:22 AM Lai Jiangshan <jiangshanlai@gmail.com> wrote:
> > >
> > > Hello
> Hi Lai,
>
> …
> > > 2) wq_worker_running() can be interrupted(async-page-faulted in virtual machine)
> > > and nr_running would be decreased twice.
> >
> > would be *increased* twice
> >
> > I just saw the V2 patch, this issue is not listed, but need to be fixed too.
>
> | void wq_worker_running(struct task_struct *task)
> | {
> | struct worker *worker = kthread_data(task);
> |
> | if (!worker->sleeping)
> | return;
> | if (!(worker->flags & WORKER_NOT_RUNNING))
> | atomic_inc(&worker->pool->nr_running);
> *0
> | worker->sleeping = 0;
> *1
> | }
>
> So an interrupt
> - before *0, the preempting caller drop early in wq_worker_sleeping(), only one
> atomic_inc()
If it is preempted on *0, the preempting caller drop early in
wq_worker_sleeping()
so there is no atomic decreasing, only one atomic_inc() in the
preempting caller.
The preempted point here, wq_worker_running(), has already just done
atomic_inc(),
the total number of atomic_inc() is two, while the number of atomic decreasing
is one.
>
> - after *1, the preempting task will invoke wq_worker_sleeping() and do
> dec() + inc().
>
> What did I miss here?
>
> Sebastian
next prev parent reply other threads:[~2020-04-02 0:07 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-27 7:43 6d25be5782 ("sched/core, workqueues: Distangle worker .."): [ 52.816697] WARNING: CPU: 0 PID: 14 at kernel/workqueue.c:882 wq_worker_sleeping kernel test robot
2020-03-27 7:43 ` kernel test robot
2020-03-27 17:53 ` [PATCH] workqueue: Don't double assign worker->sleeping Sebastian Andrzej Siewior
2020-03-27 17:53 ` Sebastian Andrzej Siewior
2020-03-27 23:29 ` [PATCH v2] workqueue: Remove the warning in wq_worker_sleeping() Sebastian Andrzej Siewior
2020-03-27 23:29 ` Sebastian Andrzej Siewior
2020-04-03 14:53 ` Tejun Heo
2020-04-03 14:53 ` Tejun Heo
2020-04-03 19:29 ` Sebastian Andrzej Siewior
2020-04-03 19:29 ` Sebastian Andrzej Siewior
2020-04-03 17:45 ` Daniel Jordan
2020-04-03 17:45 ` Daniel Jordan
2020-04-03 18:25 ` Sebastian Andrzej Siewior
2020-04-03 18:25 ` Sebastian Andrzej Siewior
2020-04-03 19:05 ` Daniel Jordan
2020-04-03 19:05 ` Daniel Jordan
2020-04-01 3:22 ` [PATCH] workqueue: Don't double assign worker->sleeping Lai Jiangshan
2020-04-01 3:44 ` Lai Jiangshan
2020-04-01 13:03 ` Sebastian Andrzej Siewior
2020-04-01 13:03 ` Sebastian Andrzej Siewior
2020-04-02 0:07 ` Lai Jiangshan [this message]
2020-04-02 7:29 ` Sebastian Andrzej Siewior
2020-04-02 7:29 ` Sebastian Andrzej Siewior
2020-04-08 12:20 ` [tip: sched/urgent] workqueue: Remove the warning in wq_worker_sleeping() tip-bot2 for Sebastian Andrzej Siewior
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