From: Pavel Begunkov <asml.silence@gmail.com>
To: Jens Axboe <axboe@kernel.dk>, io-uring@vger.kernel.org
Subject: Re: [PATCH liburing] Fix hang in in io_uring_get_cqe() with iopoll
Date: Sun, 21 Jun 2020 18:30:25 +0300 [thread overview]
Message-ID: <8e9d1846-2bb0-4827-c527-9834c9101775@gmail.com> (raw)
In-Reply-To: <b7e1f0c9-8650-d45f-5821-6c4984bec320@kernel.dk>
On 21/06/2020 18:23, Jens Axboe wrote:
> On 6/21/20 4:30 AM, Pavel Begunkov wrote:
>> Because of need_resched() check, io_uring_enter() -> io_iopoll_check()
>> can return 0 even if @min_complete wasn't satisfied. If that's the
>> case, __io_uring_get_cqe() sets submit=0 and wait_nr=0, disabling
>> setting IORING_ENTER_GETEVENTS as well. So, it goes crazy calling
>> io_uring_enter() in a loop, not actually submitting nor polling.
>>
>> Set @wait_nr based on actual number of CQEs ready.
>> BTW, atomic_load_acquire() in io_uring_cq_ready() can be replaced
>> with a relaxed one for this particular place.
>
> Can you preface this with an addition of __io_uring_cqe_ready() that
> doesn't include the load acquire?
Sure
> Also, s/io_adjut_wait_nr/io_adjust_wait_nr for the patch.
Ouch, a typo
--
Pavel Begunkov
prev parent reply other threads:[~2020-06-21 15:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-21 10:30 [PATCH liburing] Fix hang in in io_uring_get_cqe() with iopoll Pavel Begunkov
2020-06-21 15:23 ` Jens Axboe
2020-06-21 15:30 ` Pavel Begunkov [this message]
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