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Message-ID: <20200401130346.e7cdsqgxppa6ohje@linutronix.de>
Date: Wed, 1 Apr 2020 15:03:46 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Lai Jiangshan <jiangshanlai@...il.com>
Cc: kernel test robot <lkp@...el.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
LKML <linux-kernel@...r.kernel.org>, LKP <lkp@...ts.01.org>,
Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH] workqueue: Don't double assign worker->sleeping
On 2020-04-01 11:44:06 [+0800], Lai Jiangshan wrote:
> On Wed, Apr 1, 2020 at 11:22 AM Lai Jiangshan <jiangshanlai@...il.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()
- after *1, the preempting task will invoke wq_worker_sleeping() and do
dec() + inc().
What did I miss here?
Sebastian
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