From: John Ogness <john.ogness@linutronix.de>
To: Nguyen Ngoc Thang <ngocthang2710.1999@gmail.com>,
Petr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
linux-kernel@vger.kernel.org,
Nguyen Ngoc Thang <ngocthang2710.1999@gmail.com>,
syzbot+8324b8fd984b86905a66@syzkaller.appspotmail.com
Subject: Re: [PATCH v2] printk: annotate the intentional data race on the data block id
Date: Mon, 12 Oct 2026 14:40:48 +0206 [thread overview]
Message-ID: <87pkxfxfkn.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <20261012120341.12423-1-ngocthang2710.1999@gmail.com>
On 2026-10-12, Nguyen Ngoc Thang <ngocthang2710.1999@gmail.com> wrote:
> data_alloc() stores the descriptor ID into a newly reserved data block
> while data_make_reusable(), running from data_push_tail() on another CPU,
> may still be loading the ID from the same area. The ringbuffer allows
> this race: a stale or garbage ID simply fails the descriptor lookup or
> the blk_lpos check. KCSAN nevertheless reports it.
>
> Annotate the accesses with data_race() instead of READ_ONCE()/WRITE_ONCE(),
> which would needlessly restrict compiler optimizations for a race that is
> allowed by design. No functional change.
>
> Reported-by: syzbot+8324b8fd984b86905a66@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=8324b8fd984b86905a66
> Fixes: 896fbe20b4e2 ("printk: use the lockless ringbuffer")
> Signed-off-by: Nguyen Ngoc Thang <ngocthang2710.1999@gmail.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
next prev parent reply other threads:[~2026-10-12 12:34 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-12 12:03 [PATCH v2] printk: annotate the intentional data race on the data block id Nguyen Ngoc Thang
2026-10-12 12:34 ` John Ogness [this message]
2026-10-27 15:24 ` Petr Mladek
2026-10-27 15:47 ` Petr Mladek
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