From: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
To: akpm@linux-foundation.org, bhe@redhat.com, pmladek@suse.com,
feng.tang@intel.com
Cc: kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
linux-hyperv@vger.kernel.org, netdev@vger.kernel.org,
x86@kernel.org, kernel-dev@igalia.com, kernel@gpiccoli.net
Subject: Re: [PATCH V3 11/11] panic: Fixes the panic_print NMI backtrace setting
Date: Tue, 22 Nov 2022 10:35:34 -0300 [thread overview]
Message-ID: <831175d7-1b30-de61-d6c5-cbb91e4fdcfb@igalia.com> (raw)
In-Reply-To: <20220819221731.480795-12-gpiccoli@igalia.com>
On 19/08/2022 19:17, Guilherme G. Piccoli wrote:
> Commit 8d470a45d1a6 ("panic: add option to dump all CPUs backtraces in panic_print")
> introduced a setting for the "panic_print" kernel parameter to allow
> users to request a NMI backtrace on panic. Problem is that the panic_print
> handling happens after the secondary CPUs are already disabled, hence
> this option ended-up being kind of a no-op - kernel skips the NMI trace
> in idling CPUs, which is the case of offline CPUs.
>
> Fix it by checking the NMI backtrace bit in the panic_print prior to
> the CPU disabling function.
>
> Fixes: 8d470a45d1a6 ("panic: add option to dump all CPUs backtraces in panic_print")
> Cc: Feng Tang <feng.tang@intel.com>
> Cc: Petr Mladek <pmladek@suse.com>
> Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
>
> ---
>
> V3:
> - No changes.
>
> V2:
> - new patch, there was no V1 of this one.
>
> Hi folks, thanks upfront for reviews. This is a new patch, fixing an issue
> I found in my tests, so I shoved it into this fixes series.
>
> Notice that while at it, I got rid of the "crash_kexec_post_notifiers"
> local copy in panic(). This was introduced by commit b26e27ddfd2a
> ("kexec: use core_param for crash_kexec_post_notifiers boot option"),
> but it is not clear from comments or commit message why this local copy
> is required.
>
> My understanding is that it's a mechanism to prevent some concurrency,
> in case some other CPU modify this variable while panic() is running.
> I find it very unlikely, hence I removed it - but if people consider
> this copy needed, I can respin this patch and keep it, even providing a
> comment about that, in order to be explict about its need.
>
> Let me know your thoughts! Cheers,
>
> Guilherme
>
>
Hi folks, bi-monthly ping - apologies for the noise heh
Is there anything suggested so we can get this fix merged in 6.2? Any
suggestions / reviews are much appreciated.
Tnx in advance,
Guilherme
prev parent reply other threads:[~2022-11-22 14:31 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-19 22:17 [PATCH V3 00/11] The panic notifiers refactor - fixes/clean-ups (V3) Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 01/11] ARM: Disable FIQs (but not IRQs) on CPUs shutdown paths Guilherme G. Piccoli
2022-09-18 13:58 ` Guilherme G. Piccoli
2022-10-17 14:00 ` Guilherme G. Piccoli
2022-10-17 14:17 ` Russell King (Oracle)
2022-10-17 14:50 ` Guilherme G. Piccoli
2022-10-17 17:47 ` Russell King (Oracle)
2022-10-17 19:43 ` Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 02/11] notifier: Add panic notifiers info and purge trailing whitespaces Guilherme G. Piccoli
2022-11-22 13:19 ` Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 03/11] alpha: Clean-up the panic notifier code Guilherme G. Piccoli
2022-11-22 13:22 ` Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 04/11] um: Improve panic notifiers consistency and ordering Guilherme G. Piccoli
2022-09-18 14:00 ` Guilherme G. Piccoli
2022-09-18 21:19 ` Richard Weinberger
2022-09-19 11:44 ` Guilherme G. Piccoli
2022-10-17 14:01 ` Guilherme G. Piccoli
2022-10-17 14:10 ` Richard Weinberger
2022-10-17 14:22 ` Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 05/11] parisc: Replace regular spinlock with spin_trylock on panic path Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 06/11] tracing: Improve panic/die notifiers Guilherme G. Piccoli
2022-09-18 14:04 ` Guilherme G. Piccoli
2022-10-17 14:02 ` Guilherme G. Piccoli
2022-10-20 21:29 ` Steven Rostedt
2022-10-20 21:53 ` Guilherme G. Piccoli
2022-10-20 22:22 ` Steven Rostedt
2022-10-20 22:37 ` Guilherme G. Piccoli
2022-11-22 13:27 ` Guilherme G. Piccoli
2022-12-13 23:51 ` Guilherme G. Piccoli
2022-12-14 0:06 ` Steven Rostedt
2022-12-14 0:52 ` Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 07/11] notifiers: Add tracepoints to the notifiers infrastructure Guilherme G. Piccoli
2022-09-18 14:07 ` Guilherme G. Piccoli
2022-10-17 14:04 ` Guilherme G. Piccoli
2022-11-22 13:30 ` Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 08/11] EDAC/altera: Skip the panic notifier if kdump is loaded Guilherme G. Piccoli
2022-09-18 14:10 ` Guilherme G. Piccoli
2022-10-17 14:05 ` Guilherme G. Piccoli
2022-11-22 13:33 ` Guilherme G. Piccoli
2022-11-22 15:06 ` Borislav Petkov
2023-02-10 16:01 ` Guilherme G. Piccoli
2022-12-09 16:03 ` Petr Mladek
2022-08-19 22:17 ` [PATCH V3 09/11] video/hyperv_fb: Avoid taking busy spinlock on panic path Guilherme G. Piccoli
2022-09-18 14:12 ` Guilherme G. Piccoli
2022-10-04 16:17 ` Michael Kelley (LINUX)
2022-08-19 22:17 ` [PATCH V3 10/11] drivers/hv/vmbus, video/hyperv_fb: Untangle and refactor Hyper-V panic notifiers Guilherme G. Piccoli
2022-10-04 16:24 ` Michael Kelley (LINUX)
2022-10-04 17:20 ` Guilherme G. Piccoli
2022-10-17 15:26 ` Michael Kelley (LINUX)
2022-11-10 21:32 ` Guilherme G. Piccoli
2022-11-11 22:47 ` Wei Liu
2022-11-11 23:16 ` Wei Liu
2022-11-12 21:53 ` Guilherme G. Piccoli
2022-08-19 22:17 ` [PATCH V3 11/11] panic: Fixes the panic_print NMI backtrace setting Guilherme G. Piccoli
2022-09-18 14:13 ` Guilherme G. Piccoli
2022-11-22 13:35 ` Guilherme G. Piccoli [this message]
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