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

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Message-ID: <87y1xkwa28.fsf@email.froward.int.ebiederm.org>
Date:   Sat, 25 Jun 2022 19:19:27 -0500
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Christian Brauner <brauner@...nel.org>, Tejun Heo <tj@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Michal Hocko <mhocko@...e.com>,
        Linux Kernel Mailing List <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>,
        Oleg Nesterov <oleg@...hat.com>
Subject: Re: re. Spurious wakeup on a newly created kthread


Linus Torvalds <torvalds@...ux-foundation.org> writes:

> Anyway, the whole "don't wake up thread until it's all done" is a
> separate and independent issue from the "odd use of kthreadd" issue.

Yes.  "don't wake up a kthread until it's all done" is a much easier
change that will simplify things tremendously.

Further it is necessary for Peter Zijlstra's rewrite of the kernel
freezer.   As anything that isn't a special stop state (which
TASK_UNINTERRUPTIBLE is not) will receive a spurious wake up on when
thawed out.

Eric