Re: [syzbot] INFO: task hung in io_sq_thread_park (2)
From: Pavel Begunkov <asml.silence@gmail.com>
Date: 2021-07-19 18:27:16
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On 7/19/21 6:13 PM, Jens Axboe wrote:
On 7/19/21 10:57 AM, Pavel Begunkov wrote:quoted
On 7/16/21 11:57 AM, syzbot wrote:quoted
Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: WARNING in io_uring_cancel_generic__arm_poll doesn't remove a second poll entry in case of failed __io_queue_proc(), it's most likely the cause here. #syz test: https://github.com/isilence/linux.git syztest_sqpoll_hangWas my thought on seeing the last debug run too. Haven't written a test case, but my initial thought was catching this at the time that double poll is armed, in __io_queue_proc(). Totally untested, just tossing it out there.
Wouldn't help, unfortunately, the way syz triggers it is making a request to go through __io_queue_proc() three times. Either it's 3 waitqueues or we need to extend the check below to the double poll entry. if (poll_one->head == head) return;
quoted hunk ↗ jump to hunk
diff --git a/fs/io_uring.c b/fs/io_uring.c index 0cac361bf6b8..ed33de5fffd2 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c@@ -5002,6 +5002,9 @@ static void __io_queue_proc(struct io_poll_iocb *poll, struct io_poll_table *pt, if (unlikely(poll->head)) { struct io_poll_iocb *poll_one = poll; + /* first poll failed, don't arm double poll */ + if (pt->error) + return; /* already have a 2nd entry, fail a third attempt */ if (*poll_ptr) { pt->error = -EINVAL;
-- Pavel Begunkov