linux-kernel - Re: [PATCH v2 2/2] Allow cpu backtraces to be written into ringbuffer during panic

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Message-ID: <ZrDY90xLj50CJ-jG@pathway.suse.cz>
Date: Mon, 5 Aug 2024 15:51:51 +0200
From: Petr Mladek <pmladek@...e.com>
To: takakura@...inux.co.jp
Cc: rostedt@...dmis.org, john.ogness@...utronix.de,
	senozhatsky@...omium.org, akpm@...ux-foundation.org, bhe@...hat.com,
	lukas@...ner.de, wangkefeng.wang@...wei.com, ubizjak@...il.com,
	feng.tang@...el.com, j.granados@...sung.com,
	stephen.s.brennan@...cle.com, linux-kernel@...r.kernel.org,
	nishimura@...inux.co.jp, taka@...inux.co.jp
Subject: Re: [PATCH v2 2/2] Allow cpu backtraces to be written into
 ringbuffer during panic

On Sat 2024-08-03 17:16:49, takakura@...inux.co.jp wrote:
> From: Ryo Takakura <takakura@...inux.co.jp>
> 
> commit 779dbc2e78d7 ("printk: Avoid non-panic CPUs writing
> to ringbuffer") disabled non-panic CPUs to further write messages to
> ringbuffer after panicked.
> 
> Since the commit, non-panicked CPU's are not allowed to write to
> ring buffer after panicked and CPU backtrace which is triggered
> after panicked to sample non-panicked CPUs' backtrace no longer
> serves its function as it has nothing to print.
> 
> Fix the issue by allowing non-panicked CPUs to write into ringbuffer
> while CPU backtrace is in flight.
> 
> Fixes: 779dbc2e78d7 ("printk: Avoid non-panic CPUs writing to ringbuffer")
> Signed-off-by: Ryo Takakura <takakura@...inux.co.jp>

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr