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Tue, 27 Oct 2026 08:47:35 -0700 (PDT) Received: from pathway.suse.cz ([176.114.240.130]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48e3ecdfd8dsm21964926f8f.56.2026.10.27.08.47.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Oct 2026 08:47:35 -0700 (PDT) Date: Tue, 27 Oct 2026 16:47:33 +0100 From: Petr Mladek To: Nguyen Ngoc Thang Cc: Steven Rostedt , John Ogness , Sergey Senozhatsky , linux-kernel@vger.kernel.org, syzbot+8324b8fd984b86905a66@syzkaller.appspotmail.com Subject: Re: [PATCH v2] printk: annotate the intentional data race on the data block id Message-ID: References: <20261012120341.12423-1-ngocthang2710.1999@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261012120341.12423-1-ngocthang2710.1999@gmail.com> On Mon 2026-10-12 19:03:39, Nguyen Ngoc Thang 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 JFYI, the patch has been committed into printk/linux.git, branch for-7.5-trivial. Best Regards, Petr