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Tue, 02 Mar 2021 09:20:06 -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: <000000000000a52fb105bc71e7b8@google.com> From: Jens Axboe Message-ID: <586d357d-8c4c-8875-3a1c-0599a0a64da0@kernel.dk> Date: Tue, 2 Mar 2021 10:20:05 -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: <000000000000a52fb105bc71e7b8@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 2/28/21 9:18 PM, 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 > 5.11.0-syzkaller #0 Not tainted > -------------------------------------------- > syz-executor.0/10241 is trying to acquire lock: > ffff888012e09130 (&runtime->sleep){..-.}-{2:2}, at: spin_lock include/linux/spinlock.h:354 [inline] > ffff888012e09130 (&runtime->sleep){..-.}-{2:2}, at: io_poll_double_wake+0x25f/0x6a0 fs/io_uring.c:4921 > > but task is already holding lock: > ffff888013b00130 (&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); > > *** DEADLOCK *** > > May be due to missing lock nesting notation Since the fix is in yet this keeps failing (and I didn't get it), I looked closer at this report. While the names of the locks are the same, they are really two different locks. So let's try this... #syz test: git://git.kernel.dk/linux-block syzbot-test -- Jens Axboe