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Date:   Thu, 21 Oct 2021 13:12:29 -0700
From:   Kees Cook <>
To:     Andy Lutomirski <>
Cc:     "Peter Zijlstra (Intel)" <>,
        Mark Rutland <>,
        Shuah Khan <>,
        Alexey Dobriyan <>,,
        Josh Poimboeuf <>,
        Andrew Morton <>,
        Alexey Gladkov <>,
        Jann Horn <>,
        Vito Caputo <>,
        Ingo Molnar <>,,,,
        Steven Rostedt <>,
        Ben Segall <>,,,
        Christian Brauner <>,,,,, Michal Hocko <>,, Qi Zheng <>,,, Thomas Gleixner <>,
        Borislav Petkov <>,
        "H. Peter Anvin" <>, Jens Axboe <>,, Lai Jiangshan <>,
        Dave Hansen <>,
        "Eric W. Biederman" <>,,,,,, "Russell King (Oracle)" <>,
        Will Deacon <>,,,,,,,
        Michael Ellerman <>,
        Paul Walmsley <>,,,,,
        Linux Kernel Mailing List <>,,
Subject: Re: [PATCH] selftests: proc: Make sure wchan works when it exists

On Thu, Oct 21, 2021 at 01:03:33PM -0700, Andy Lutomirski wrote:
> On Fri, Oct 8, 2021, at 4:55 PM, Kees Cook wrote:
> > This makes sure that wchan contains a sensible symbol when a process is
> > blocked. Specifically this calls the sleep() syscall, and expects the
> > architecture to have called schedule() from a function that has "sleep"
> > somewhere in its name. For example, on the architectures I tested
> > (x86_64, arm64, arm, mips, and powerpc) this is "hrtimer_nanosleep":
> Is this really better than admitting that the whole mechanism is nonsense and disabling it?
> We could have a fixed string for each task state and call it a day.

I consider this to be "future work". In earlier discussions it came up,
but there wasn't an obvious clean cost-free way to do this, so instead
we're just fixing the broken corner and keeping the mostly working rest
of it while cleaning up the weird edges. :)

Kees Cook

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