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References: <20161025182742.10486-1-roman.penyaev@profitbricks.com> <20161026141834.GB6893@redhat.com>
From: Roman Penyaev <roman.penyaev@profitbricks.com>
Date: Wed, 26 Oct 2016 17:43:55 +0200
Message-ID: <CAJrWOzA-7fDv3shn1iC9puWSruYc--x0mKdqzyRESY6MBj+GsQ@mail.gmail.com>
Subject: Re: [PATCH v4 1/1] workqueue: ignore dead tasks in a workqueue sleep hook
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        Tejun Heo <tj@kernel.org>, linux-kernel@vger.kernel.org
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On Wed, Oct 26, 2016 at 4:18 PM, Oleg Nesterov <oleg@redhat.com> wrote:
> On 10/25, Roman Pen wrote:
>>
>>  void wq_worker_waking_up(struct task_struct *task, int cpu)
>>  {
>> -     struct worker *worker = kthread_data(task);
>> +     struct worker *worker;
>> +
>> +     if (task->flags & PF_EXITING) {
>> +             /*
>> +              * Careful here, t->vfork_done is zeroed out for
>> +              * almost dead tasks, do not touch kthread_data().
>> +              */
>> +             return;
>> +     }
>> +
>> +     worker = kthread_data(task);
>>
>>       if (!(worker->flags & WORKER_NOT_RUNNING)) {
>>               WARN_ON_ONCE(worker->pool->cpu != cpu);
>> @@ -875,9 +885,19 @@ void wq_worker_waking_up(struct task_struct *task, int cpu)
>>   */
>>  struct task_struct *wq_worker_sleeping(struct task_struct *task)
>>  {
>> -     struct worker *worker = kthread_data(task), *to_wakeup = NULL;
>> +     struct worker *worker, *to_wakeup = NULL;
>>       struct worker_pool *pool;
>>
>> +     if (task->flags & PF_EXITING) {
>> +             /*
>> +              * Careful here, t->vfork_done is zeroed out for
>> +              * almost dead tasks, do not touch kthread_data().
>> +              */
>> +             return NULL;
>> +     }
>> +
>> +     worker = kthread_data(task);
>> +
>
> Please see the patch I send a minute ago. With that patch we do not need
> this fix, kthread_data() no longer uses ->vfork_done.

Perfect. Thanks.  Oleg, could you please add me to CC when you finally send
a patch.

--
Roman