From: Jens Axboe <axboe@kernel.dk>
To: yaozhenguo <yaozhenguo1@gmail.com>, oleg@redhat.comm
Cc: linux-kernel@vger.kernel.org, yaozhenguo@jd.com
Subject: Re: [PATCH] task_work: return -EBUSY when adding same work
Date: Fri, 9 Jul 2021 08:18:27 -0600 [thread overview]
Message-ID: <872612b5-b9c6-43aa-a167-1c204d0f1c5a@kernel.dk> (raw)
In-Reply-To: <20210709122712.42844-1-yaozhenguo1@gmail.com>
On 7/9/21 6:27 AM, yaozhenguo wrote:
> when same work is added to task->task_works list one by one,
> the list becomes endless loop. So return -EBUSY when this
> situation happen.
>
> Signed-off-by: yaozhenguo <yaozhenguo1@gmail.com>
> ---
> kernel/task_work.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/task_work.c b/kernel/task_work.c
> index 1698fbe..5061ebf 100644
> --- a/kernel/task_work.c
> +++ b/kernel/task_work.c
> @@ -27,7 +27,7 @@
> * list is LIFO.
> *
> * RETURNS:
> - * 0 if succeeds or -ESRCH.
> + * 0 if succeeds or -ESRCH, -EBUSY.
> */
> int task_work_add(struct task_struct *task, struct callback_head *work,
> enum task_work_notify_mode notify)
> @@ -41,6 +41,8 @@ int task_work_add(struct task_struct *task, struct callback_head *work,
> head = READ_ONCE(task->task_works);
> if (unlikely(head == &work_exited))
> return -ESRCH;
> + if (unlikely(head == work))
> + return -EBUSY;
> work->next = head;
> } while (cmpxchg(&task->task_works, head, work) != head);
I don't think there's anything conceptually wrong with this patch, but
it makes me think that you hit this condition. It's really a bug in the
caller, of course, is a WARN_ON_ONCE() warranted here? And who was the
caller?
--
Jens Axboe
next prev parent reply other threads:[~2021-07-09 14:18 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-09 12:27 [PATCH] task_work: return -EBUSY when adding same work yaozhenguo
2021-07-09 14:18 ` Jens Axboe [this message]
[not found] ` <CA+WzARnFgohHZ=BhL4OaCagB_c1uB6a=Bv7vM_zRUJeANHksEg@mail.gmail.com>
2021-07-12 2:44 ` Jens Axboe
2021-07-12 3:45 ` zhenguo yao
2021-07-12 9:08 ` zhenguo yao
2021-07-13 10:41 ` David Laight
2021-07-13 20:22 ` Jens Axboe
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