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SubjectRe: [PATCH v3 1/1] workqueue: ignore dead tasks in a workqueue sleep hook
On Tue, Oct 25, 2016 at 2:56 PM, Oleg Nesterov <oleg@redhat.com> wrote:
> On 10/25, Roman Pen wrote:
>>
>> 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->state == TASK_DEAD) {
>> + /*
>> + * Here we try to catch the following path before
>> + * accessing NULL kthread->vfork_done ptr thru
>> + * kthread_data():
>> + *
>> + * oops_end()
>> + * do_exit()
>> + * schedule()
>> + *
>> + * If panic_on_oops is not set and oops happens on
>> + * a workqueue execution path, thread will be killed.
>> + * That is definitly sad, but not to make the situation
>> + * even worse we have to ignore dead tasks in order not
>> + * to step on zeroed out members (e.g. t->vfork_done is
>> + * already NULL on that path, since we were called by
>> + * do_exit())).
>> + */
>> + return NULL;
>> + }
>
> I still think that PF_EXITING check makes more sense than TASK_DEAD,
> but I won't insist.

Why? I probably do not see the corner cases, so, please, explain.

--
Roman

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