Re: [PATCH v2] kernel/kthread.c: kthread_worker: add work status check in timer_fn

[Petr Mladek <pmladek@suse.com>]

On Fri 2020-09-25 13:07:59, qiang.zhang@windriver.com wrote:
> From: Zqiang <qiang.zhang@windriver.com>
> 
> When queue delayed work to worker, at some point after that the timer_fn
> will be call, add work to worker's work_list, at this time, the work may
> be cancel, so add "work->canceling" check current work status.

Great catch!

I was able to understand the problem from the description. Though I
would still try to improve it a bit. I suggest:

<new_text>
Subject: kthread_worker: Prevent queuing delayed work from timer_fn when it is being canceled

There is a small race window when a delayed work is being canceled and
the work still might be queued from the timer_fn:

CPU0					CPU1

kthread_cancel_delayed_work_sync()
  __kthread_cancel_work_sync()
    __kthread_cancel_work()
	work->canceling++;

					kthread_delayed_work_timer_fn()
					  kthread_insert_work();

BUG: kthread_insert_work() should not get called when work->canceling
is set.
</new_text>

> Signed-off-by: Zqiang <qiang.zhang@windriver.com>

With the above subject and commit message:

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr