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From: Oleg Nesterov <oleg@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: io-uring@vger.kernel.org, viro@zeniv.linux.org.uk,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 4/4] io_uring: flush task work before waiting for ring exit
Date: Wed, 8 Apr 2020 22:17:35 +0200	[thread overview]
Message-ID: <20200408201734.GA21347@redhat.com> (raw)
In-Reply-To: <6d320b43-254d-2d42-cbad-d323f1532e65@kernel.dk>

On 04/08, Jens Axboe wrote:
>
> Here's some more data. I added a WARN_ON_ONCE() for task->flags &
> PF_EXITING on task_work_add() success, and it triggers with the
> following backtrace:
...
> which means that we've successfully added the task_work while the
> process is exiting.

but this is fine, task_work_add(task) can succeed if task->flags & EXITING.

task_work_add(task, work) should only fail if this "task" has already passed
exit_task_work(). Because if this task has already passed exit_task_work(),
nothing else can flush this work and call work->func().

Oleg.


  reply	other threads:[~2020-04-08 20:17 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-07 16:02 [PATCHSET v2] io_uring and task_work interactions Jens Axboe
2020-04-07 16:02 ` [PATCH 1/4] task_work: add task_work_pending() helper Jens Axboe
2020-04-07 17:52   ` Jann Horn
2020-04-07 16:02 ` [PATCH 2/4] task_work: kill current->task_works checking in callers Jens Axboe
2020-04-07 16:02 ` [PATCH 3/4] task_work: make exit_work externally visible Jens Axboe
2020-04-07 16:02 ` [PATCH 4/4] io_uring: flush task work before waiting for ring exit Jens Axboe
2020-04-07 16:24   ` Oleg Nesterov
2020-04-07 16:38     ` Oleg Nesterov
2020-04-07 20:30       ` Jens Axboe
2020-04-07 20:39         ` Jens Axboe
2020-04-08 18:40         ` Oleg Nesterov
2020-04-08 18:48           ` Jens Axboe
2020-04-08 19:06             ` Jens Axboe
2020-04-08 20:17               ` Oleg Nesterov [this message]
2020-04-08 20:25                 ` Jens Axboe
2020-04-08 21:19                   ` Jens Axboe
2020-04-09 18:50                   ` Oleg Nesterov
2020-04-10  0:29                     ` Jens Axboe
  -- strict thread matches above, loose matches on Subject: below --
2020-04-06 19:48 [PATCHSET 0/4] io_uring and task_work interactions Jens Axboe
2020-04-06 19:48 ` [PATCH 4/4] io_uring: flush task work before waiting for ring exit Jens Axboe

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