Sched_ext development
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From: Tejun Heo <tj@kernel.org>
To: Joel Fernandes <joelagnelf@nvidia.com>
Cc: linux-kernel@vger.kernel.org, David Vernet <void@manifault.com>,
	Andrea Righi <arighi@nvidia.com>,
	Changwoo Min <changwoo@igalia.com>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Valentin Schneider <vschneid@redhat.com>,
	sched-ext@lists.linux.dev
Subject: Re: [RFT] sched_ext: Skip stack trace capture in NMI context
Date: Mon, 22 Dec 2025 16:44:21 -1000	[thread overview]
Message-ID: <aUoCBVhHig737uKt@slm.duckdns.org> (raw)
In-Reply-To: <20251223005038.62406-1-joelagnelf@nvidia.com>

Hello,

On Mon, Dec 22, 2025 at 07:50:37PM -0500, Joel Fernandes wrote:
> stack_trace_save() is not guaranteed to be NMI-safe on all
> architectures.
> 
> The hardlockup detector calls into sched_ext via the following call
> chain when an NMI occurs:
> 
>   watchdog_overflow_callback()
>     watchdog_hardlockup_check()
>       scx_hardlockup()
>         stack_trace_save()
> 
> Skip stack trace capture when in_nmi() returns true to prevent
> potential deadlocks.
> 
> Fixes: 582f700e1bdc ("sched_ext: Hook up hardlockup detector")
> Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>

This does work on x86 (right?) and is useful in understanding what the
underlying problem is. It'd be great if there's a config flag we can test
but if not can we specifically exclude archs which are known to not work?

Thanks.

-- 
tejun

  reply	other threads:[~2025-12-23  2:44 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-12-23  0:50 [RFT] sched_ext: Skip stack trace capture in NMI context Joel Fernandes
2025-12-23  2:44 ` Tejun Heo [this message]
2025-12-23  4:34   ` Joel Fernandes
2025-12-23 20:31     ` Steven Rostedt
2025-12-23 23:58       ` Joel Fernandes
2025-12-24 14:18         ` Steven Rostedt
2025-12-24 17:42           ` Joel Fernandes
2025-12-23  6:39 ` Andrea Righi

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