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@xxxxxxxxx>
> Cc: Petr Mladek <pmladek@xxxxxxxx>
> Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx>
>
> ---
>
> 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
