linux-kernel - Re: [PATCH v3 1/2] Allow cpu backtraces to be written into ringbuffer during panic

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Message-Id: <20240815104108.48576-1-takakura@valinux.co.jp>
Date: Thu, 15 Aug 2024 19:41:08 +0900
From: takakura@...inux.co.jp
To: pmladek@...e.com,
	john.ogness@...utronix.de
Cc: akpm@...ux-foundation.org,
	bhe@...hat.com,
	feng.tang@...el.com,
	j.granados@...sung.com,
	linux-kernel@...r.kernel.org,
	lukas@...ner.de,
	nishimura@...inux.co.jp,
	rostedt@...dmis.org,
	senozhatsky@...omium.org,
	stephen.s.brennan@...cle.com,
	taka@...inux.co.jp,
	takakura@...inux.co.jp,
	ubizjak@...il.com,
	wangkefeng.wang@...wei.com
Subject: Re: [PATCH v3 1/2] Allow cpu backtraces to be written into ringbuffer during panic

Hi Petr and John,

On Tue 2024-08-13 13:48, Petr Mladek wrote:
>On Mon 2024-08-12 16:27:03, 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>
>
>JFYI, I have pushed this patch into printk/linux.git, branch for-6.11-fixup.
>I am going to create pull request after it spends at least one or two
>days in linux-next.

Thanks!!

>The 2nd patch is more complicated. It depends on another patchset
>integrating con->write_atomic() callback. 
>
>Best Regards,
>Petr

Sincerely,
Ryo Takakura