Re: [patch 17/18] sched: Enable might_sleep() checks early

From	Steven Rostedt <rostedt@goodmis.org>
Newsgroups	linux.kernel
Subject	Re: [patch 17/18] sched: Enable might_sleep() checks early
Date	2017-05-16 15:20 +0200
Message-ID	<tHKym-65Z-13@gated-at.bofh.it> (permalink)
References	(1 earlier) <tH6AW-56V-11@gated-at.bofh.it> <tHpWV-1pB-3@gated-at.bofh.it> <tHtHc-3KQ-9@gated-at.bofh.it> <tHEVX-2xx-9@gated-at.bofh.it> <tHFfk-2DH-15@gated-at.bofh.it>
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On Tue, 16 May 2017 09:33:52 +0200 (CEST)
Thomas Gleixner <tglx@linutronix.de> wrote:


> Darn, forgot about PREEMPT_VOLUNTARY and that excellent changelog does not
> mention it either. 
> 
> > So if we schedule to the kernel_init() task before we set kthreadd_task
> > we'll try and spawn kthreads and OOPS.  
> 
> So back to Stevens question. No, we can't set the state earlier than right
> before schedule() simply because with PREEMPT preemption _is_ actually
> disabled and kernel_kthread() will trigger might_sleep() splats.

So a comment in the code mentioning PREEMPT_VOLUNTARY might be
advantageous.

> 
> What a mess.

Indeed.

-- Steve

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[patch 17/18] sched: Enable might_sleep() checks early Thomas Gleixner <tglx@linutronix.de> - 2017-05-14 20:40 +0200
  Re: [patch 17/18] sched: Enable might_sleep() checks early Steven Rostedt <rostedt@goodmis.org> - 2017-05-15 17:20 +0200
    Re: [patch 17/18] sched: Enable might_sleep() checks early Thomas Gleixner <tglx@linutronix.de> - 2017-05-15 21:20 +0200
      Re: [patch 17/18] sched: Enable might_sleep() checks early Peter Zijlstra <peterz@infradead.org> - 2017-05-16 09:20 +0200
        Re: [patch 17/18] sched: Enable might_sleep() checks early Thomas Gleixner <tglx@linutronix.de> - 2017-05-16 09:40 +0200
          Re: [patch 17/18] sched: Enable might_sleep() checks early Steven Rostedt <rostedt@goodmis.org> - 2017-05-16 15:20 +0200

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