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

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Date:   Tue, 24 Mar 2020 10:30:02 +0100
From:   Jann Horn <jannh@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>
Cc:     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 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?