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Tue, 02 Mar 2021 20:01:47 -0800 (PST) Subject: Re: possible deadlock in io_poll_double_wake (2) To: syzbot , asml.silence@gmail.com, io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk References: <00000000000017349305bc9254f4@google.com> From: Jens Axboe Message-ID: Date: Tue, 2 Mar 2021 21:01:45 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <00000000000017349305bc9254f4@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 3/2/21 11:59 AM, syzbot wrote: > Hello, > > syzbot has tested the proposed patch but the reproducer is still triggering an issue: > possible deadlock in io_poll_double_wake > > ============================================ > WARNING: possible recursive locking detected > 5.12.0-rc1-syzkaller #0 Not tainted > -------------------------------------------- > syz-executor.4/10454 is trying to acquire lock: > ffff8880343cc130 (&runtime->sleep){..-.}-{2:2}, at: spin_lock include/linux/spinlock.h:354 [inline] > ffff8880343cc130 (&runtime->sleep){..-.}-{2:2}, at: io_poll_double_wake+0x25f/0x6a0 fs/io_uring.c:4925 > > but task is already holding lock: > ffff888034e3b130 (&runtime->sleep){..-.}-{2:2}, at: __wake_up_common_lock+0xb4/0x130 kernel/sched/wait.c:137 > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&runtime->sleep); > lock(&runtime->sleep); This still makes no sense to me - naming is the same, but address of waitqueue_head is not (which is what matters). Unless I'm missing something obvious here. Anyway, added some debug printks, so let's try again. #syz test: git://git.kernel.dk/linux-block syzbot-test -- Jens Axboe