linux-kernel - Re: re. Spurious wakeup on a newly created kthread

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Message-ID: <YrmEBjtIu/4TOaQ/@dhcp22.suse.cz>
Date:   Mon, 27 Jun 2022 12:18:46 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Petr Mladek <pmladek@...e.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: re. Spurious wakeup on a newly created kthread

On Mon 27-06-22 17:21:12, Tejun Heo wrote:
> Hello, Michal.
> 
> On Mon, Jun 27, 2022 at 10:07:22AM +0200, Michal Hocko wrote:
> > So if somebody has woken up our thread from inside kthread() then it
> > doesn't have that pointer on the stack and I couldn't it find elsewhere
> > either. Maybe somebody has an idea where to look at.
> 
> One way could be bpftrace'ing or printking __wake_up_common() and
> friends to dump backtrace if it's trying to wake a kthread whose comm
> starts with kworker/ and doesn't have (struct worker
> *)kthread_data(task)->pool set.

I am afraid I won't have a chance for a runtime debugging. All I have at
this stage is a crash dump.
-- 
Michal Hocko
SUSE Labs