From: Petr Mladek <pmladek@suse.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tejun Heo <tj@kernel.org>, Lai Jiangshan <jiangshanlai@gmail.com>,
Michal Hocko <mhocko@suse.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Oleg Nesterov <oleg@redhat.com>,
"Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: re. Spurious wakeup on a newly created kthread
Date: Tue, 28 Jun 2022 11:51:37 +0200 [thread overview]
Message-ID: <YrrPKU2y4liY91u9@alley> (raw)
In-Reply-To: <CAHk-=wiC7rj1o7vTnYUPfD7YxAu09MZiZbahHqvLm9+Cgg1dFw@mail.gmail.com>
On Sat 2022-06-25 10:01:35, Linus Torvalds wrote:
> On Fri, Jun 24, 2022 at 10:00 PM Tejun Heo <tj@kernel.org> wrote:
> For example, the reason that quoted patch cannot be right is that this
> code pattern:
>
> while (wait_for_completion_interruptible(&worker->ready_to_start))
> ;
>
> is not valid kernel code. EVER. There is absolutely no way that can be correct.
>
> Either that code can take a signal, or it cannot. If it can take a
> signal, it had better react to said signal. If it cannot, it must not
> use an interruptble sleep - since now that loop turned into a
> kernel-side busy-loop.
I agree that the code is ugly and does not make sense.
JFYI, I did it this way because I wanted to calm down the hung task
detector. kthreads ignore signals so that I did not think about
this aspect. I though that I saw this trick somewhere.
Do not ask me why I wanted to calm down the hung task detector.
I quess that I felt overloaded and wished a calm day
or something like this. I agree that it does not make
much sense.
Best Regards,
Petr
next prev parent reply other threads:[~2022-06-28 9:51 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-22 14:08 [PATCH] workqueue: Make create_worker() safe against spurious wakeups Petr Mladek
2022-06-23 7:00 ` Petr Mladek
2022-06-23 7:14 ` Michal Hocko
2022-06-25 5:00 ` re. Spurious wakeup on a newly created kthread Tejun Heo
2022-06-25 17:01 ` Linus Torvalds
2022-06-25 17:36 ` Eric W. Biederman
2022-06-25 18:25 ` Linus Torvalds
2022-06-25 18:43 ` Linus Torvalds
2022-06-25 23:28 ` Eric W. Biederman
2022-06-25 23:41 ` Eric W. Biederman
2022-06-25 23:43 ` Linus Torvalds
2022-06-25 23:48 ` Linus Torvalds
2022-06-26 0:19 ` Eric W. Biederman
2022-06-27 0:01 ` Wedson Almeida Filho
2022-06-27 7:11 ` Peter Zijlstra
2022-06-27 18:23 ` Wedson Almeida Filho
2022-06-27 18:45 ` Linus Torvalds
2022-06-26 19:14 ` [PATCH 0/3] kthread: Stop using TASK_UNINTERRUPTIBLE Eric W. Biederman
2022-06-26 19:15 ` [PATCH 1/3] kthread: Remove the flags argument from kernel_thread Eric W. Biederman
2022-06-26 21:20 ` Linus Torvalds
2022-06-26 19:16 ` [PATCH 2/3] kthread: Replace kernel_thread with new_kthread Eric W. Biederman
2022-06-26 19:16 ` [PATCH 3/3] kthread: Stop abusing TASK_UNINTERRUPTIBLE (INCOMPLETE) Eric W. Biederman
2022-06-26 19:59 ` Linus Torvalds
2022-06-26 20:23 ` Tejun Heo
2022-06-26 20:55 ` Linus Torvalds
2022-06-27 7:22 ` Peter Zijlstra
2022-06-27 8:11 ` Tejun Heo
2022-06-27 18:04 ` Wedson Almeida Filho
2022-06-27 22:06 ` Peter Zijlstra
2022-06-27 22:34 ` Linus Torvalds
2022-06-27 22:45 ` Wedson Almeida Filho
2022-06-28 0:32 ` Wedson Almeida Filho
2022-06-28 7:58 ` Peter Zijlstra
2022-06-30 0:57 ` Wedson Almeida Filho
2022-06-26 22:14 ` kernel test robot
2022-06-26 22:34 ` kernel test robot
2022-06-26 0:21 ` re. Spurious wakeup on a newly created kthread Eric W. Biederman
2022-06-28 14:16 ` Christian Brauner
2022-06-26 0:26 ` Eric W. Biederman
2022-06-26 1:58 ` Tejun Heo
2022-06-26 2:53 ` Linus Torvalds
2022-06-26 6:09 ` Tejun Heo
2022-06-27 12:04 ` Michal Hocko
2022-06-28 9:51 ` Petr Mladek [this message]
2022-06-28 10:07 ` Tejun Heo
2022-06-27 8:07 ` Michal Hocko
2022-06-27 8:21 ` Tejun Heo
2022-06-27 10:18 ` Michal Hocko
2022-06-28 15:08 ` Petr Mladek
2022-08-04 8:57 ` [PATCH] workqueue: Make create_worker() safe against spurious wakeups Lai Jiangshan
2022-08-04 10:19 ` Lai Jiangshan
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