From: Joel Fernandes <joelagnelf@nvidia.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Tejun Heo <tj@kernel.org>,
"linux-kernel@vger.kernel.org" <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>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
"sched-ext@lists.linux.dev" <sched-ext@lists.linux.dev>
Subject: Re: [RFT] sched_ext: Skip stack trace capture in NMI context
Date: Wed, 24 Dec 2025 17:42:15 +0000 [thread overview]
Message-ID: <3662F4D2-C5ED-4C53-BF7C-B7B17047BFDB@nvidia.com> (raw)
In-Reply-To: <20251224091846.3851271a@gandalf.local.home>
> On Dec 24, 2025, at 9:17 AM, Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Tue, 23 Dec 2025 18:58:33 -0500
> Joel Fernandes <joelagnelf@nvidia.com> wrote:
>
>> Some documentation suggests IST is required for reliable NMI stack tracing
>> [1] [2] which 32-bit does not have.
>> ”If an interrupt or other exception is taken while the stack or other unwind
>> state is in an inconsistent state, it may not be possible to reliably unwind,
>> and it may not be possible to identify whether such unwinding will be
>> reliable. See below for examples.“
>>
>> Probably the issue happens to be more of printing garbage than crashing the
>> kernel, but I am not convinced it is stable. Hmm.
>
> Correct. It's about reliable stack traces, as live kernel patching requires
> that the stack it looks at is reliable before it can modify the code. What
> happens if it's not reliable, means it will just stop at the interrupt
> handler and you don't get to see the rest (or you'll see a bunch of
> functions with "?" in front of them).
Ah, thanks Steve for clarifying!
- Joel
>
> -- Steve
next prev parent reply other threads:[~2025-12-24 17:42 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-23 0:50 Joel Fernandes
2025-12-23 2:44 ` Tejun Heo
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 [this message]
2025-12-23 6:39 ` Andrea Righi
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