* tip-bot2 for Lukas Wunner <tip-bot2@xxxxxxxxxxxxx> wrote:
> The following commit has been merged into the core/urgent branch of tip:
>
> Commit-ID: cccd32816506cbac3a4c65d9dff51b3125ef1a03
> Gitweb: https://git.kernel.org/tip/cccd32816506cbac3a4c65d9dff51b3125ef1a03
> Author: Lukas Wunner <lukas@xxxxxxxxx>
> AuthorDate: Fri, 15 Sep 2023 09:55:39 +02:00
> Committer: Ingo Molnar <mingo@xxxxxxxxxx>
> CommitterDate: Fri, 15 Sep 2023 11:28:08 +02:00
>
> panic: Reenable preemption in WARN slowpath
>
> Commit:
>
> 5a5d7e9badd2 ("cpuidle: lib/bug: Disable rcu_is_watching() during WARN/BUG")
>
> amended warn_slowpath_fmt() to disable preemption until the WARN splat
> has been emitted.
>
> However the commit neglected to reenable preemption in the !fmt codepath,
> i.e. when a WARN splat is emitted without additional format string.
>
> One consequence is that users may see more splats than intended. E.g. a
> WARN splat emitted in a work item results in at least two extra splats:
>
> BUG: workqueue leaked lock or atomic
> (emitted by process_one_work())
>
> BUG: scheduling while atomic
> (emitted by worker_thread() -> schedule())
>
> Ironically the point of the commit was to *avoid* extra splats. ;)
>
> Fix it.
> diff --git a/kernel/panic.c b/kernel/panic.c
> index 07239d4..ffa037f 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -697,6 +697,7 @@ void warn_slowpath_fmt(const char *file, int line, unsigned taint,
> if (!fmt) {
> __warn(file, line, __builtin_return_address(0), taint,
> NULL, NULL);
> + warn_rcu_exit(rcu);
> return;
BTW., one more thing we might want to consider here is to re-enable
preemption in warn_rcu_exit() a bit more gently, without forcing a
pending reschedule, ie. preempt_enable_no_resched() or so?
Thanks,
Ingo
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