From: Steven Rostedt <rostedt@goodmis.org>
To: Zhu Jun <zhujun2@cmss.chinamobile.com>
Cc: vdonnefort@google.com, mhiramat@kernel.org,
mathieu.desnoyers@efficios.com,
linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org,
syzbot+530af6f1e5c230588975@syzkaller.appspotmail.com
Subject: Re: [PATCH] ring-buffer: Annotate the speculative iterator event copy
Date: Thu, 12 Nov 2026 05:49:27 -0500 [thread overview]
Message-ID: <20261112054927.4f80674c@fedora> (raw)
In-Reply-To: <20261111084201.80984-1-zhujun2@cmss.chinamobile.com>
On Wed, 11 Nov 2026 16:42:01 +0800
Zhu Jun <zhujun2@cmss.chinamobile.com> wrote:
> A non-consuming iterator can copy an event while the writer overwrites
> its page. The reader lock only excludes other readers, so KCSAN reports
> the memcpy() racing with event reservation.
>
> The iterator already checks the page stamp and committed size after the
> copy and retries if the writer entered the page. Mark the speculative
> copy as an intentional race; only the validated private copy is used.
>
> Fixes: 785888c544e0 ("ring-buffer: Have rb_iter_head_event() handle concurrent writer")
I agree with the change but this isn't a fix. It's just to hide a false
positive from KCSAN. You want to add a fixes tag, add the commit that
introduced KCSAN.
-- Steve
prev parent reply other threads:[~2026-11-12 10:49 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-11 8:42 Zhu Jun
2026-11-12 10:49 ` Steven Rostedt [this message]
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