linux-kernel - Re: [PATCH v2] exit: Move preemption fixup up, move blocking operations down

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Date:   Thu, 16 Apr 2020 10:52:49 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Jann Horn <jannh@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] exit: Move preemption fixup up, move blocking
 operations down

On Tue, Mar 24, 2020 at 10:30:02AM +0100, Jann Horn wrote:
> On Thu, Mar 5, 2020 at 11:07 PM Jann Horn <jannh@...gle.com> wrote:
> > With CONFIG_DEBUG_ATOMIC_SLEEP=y and CONFIG_CGROUPS=y, kernel oopses in
> > non-preemptible context look untidy; after the main oops, the kernel prints
> > a "sleeping function called from invalid context" report because
> > exit_signals() -> cgroup_threadgroup_change_begin() -> percpu_down_read()
> > can sleep, and that happens before the preempt_count_set(PREEMPT_ENABLED)
> > fixup.
> >
> > It looks like the same thing applies to profile_task_exit() and
> > kcov_task_exit().
> >
> > Fix it by moving the preemption fixup up and the calls to
> > profile_task_exit() and kcov_task_exit() down.
> >
> > Fixes: 1dc0fffc48af ("sched/core: Robustify preemption leak checks")
> > Signed-off-by: Jann Horn <jannh@...gle.com>
> > ---
> > As so often, I have no idea which tree this should go through. tip? mm?
> 
> Do the tip folks want to take this, since it's vaguely locking-related
> and the fixed commit also came that way? Or should it go through
> akpm's tree?

I've picked it up, as it seems to be languishing. Thanks!