linux-kernel - Re: [PATCH 5.10-rt] printk: fix suppressed message print when reboot/panic

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Date:   Mon, 21 Mar 2022 10:36:55 +0106
From:   John Ogness <john.ogness@...utronix.de>
To:     Schspa Shi <schspa@...il.com>, pmladek@...e.com,
        sergey.senozhatsky@...il.com, rostedt@...dmis.org
Cc:     linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        bigeasy@...utronix.de, tglx@...utronix.de, schspa@...il.com
Subject: Re: [PATCH 5.10-rt] printk: fix suppressed message print when
 reboot/panic

On 2022-03-21, Schspa Shi <schspa@...il.com> wrote:
> Update printk_seq for suppressed message.
>
> Affects 5.9-rt and 5.10-rt
>
> When message is suppressed, printk_seq should be updated, otherwise
> this message will be printed when reboot. This problem was introduced
> in commit 3edc0c85d154 ("printk: Rebase on top of new ring buffer").
>
> Signed-off-by: Schspa Shi <schspa@...il.com>

Reviewed-by: John Ogness <john.ogness@...utronix.de>

Nice catch. Thanks.

5.15-rt also has this issue, although the fix is slightly different. For
5.15-rt, writing to con->printk_seq (via latched_seq_write()) requires
the console locked. Would you like to post a patch for 5.15-rt as well,
or would you like me to do it?

5.16 and beyond does not have this issue.

John Ogness