From: Andrew Morton <akpm@linux-foundation.org>
To: Bradley Morgan <include@grrlz.net>
Cc: pmladek@suse.com, feng.tang@linux.alibaba.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] panic: stop CPUs that lose the panic_redirect_cpu race
Date: Tue, 7 Jul 2026 11:12:56 -0700 [thread overview]
Message-ID: <20260707111256.d16cd0fba685c7fa1c1663df@linux-foundation.org> (raw)
In-Reply-To: <20260707172252.4842-1-include@grrlz.net>
On Tue, 7 Jul 2026 17:22:52 +0000 Bradley Morgan <include@grrlz.net> wrote:
> Loser of the redirect cmpxchg must stop, not fall through to
> panic_try_start().
>
> This issue was found by sashiko [1].
>
> [1] https://sashiko.dev/#/patchset/20260705164123.18746-1-include%40grrlz.net
>
> ...
>
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -400,12 +400,9 @@ static bool panic_try_force_cpu(const char *fmt, va_list args)
> if (panic_in_progress())
> return false;
>
> - /*
> - * Only one CPU can do the redirect. Use atomic cmpxchg to ensure
> - * we don't race with another CPU also trying to redirect.
> - */
> + /* Only one CPU redirects, the loser stops and lets it finish. */
> if (!atomic_try_cmpxchg(&panic_redirect_cpu, &old_cpu, this_cpu))
> - return false;
> + return true;
>
> /*
> * Use dynamically allocated buffer if available, otherwise
Sashiko is at it again:
https://sashiko.dev/#/patchset/20260707172252.4842-1-include@grrlz.net
next prev parent reply other threads:[~2026-07-07 18:12 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-07 17:22 [PATCH] panic: stop CPUs that lose the panic_redirect_cpu race Bradley Morgan
2026-07-07 18:12 ` Andrew Morton [this message]
2026-07-07 18:15 ` Bradley Morgan
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