From: Jens Axboe <[email protected]>
To: Pavel Begunkov <[email protected]>
Cc: [email protected], io-uring <[email protected]>
Subject: Re: [PATCH 5.10 1/5] io_uring: always let io_iopoll_complete() complete polled io.
Date: Tue, 8 Dec 2020 12:17:08 -0700 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 12/8/20 12:12 PM, Pavel Begunkov wrote:
> On 07/12/2020 16:28, Jens Axboe wrote:
>> On Sun, Dec 6, 2020 at 3:26 PM Pavel Begunkov <[email protected]> wrote:
>>> From: Xiaoguang Wang <[email protected]>
>>>
>>> The reason is that once we got a non EAGAIN error in io_wq_submit_work(),
>>> we'll complete req by calling io_req_complete(), which will hold completion_lock
>>> to call io_commit_cqring(), but for polled io, io_iopoll_complete() won't
>>> hold completion_lock to call io_commit_cqring(), then there maybe concurrent
>>> access to ctx->defer_list, double free may happen.
>>>
>>> To fix this bug, we always let io_iopoll_complete() complete polled io.
>>
>> This patch is causing hangs with iopoll testing, if you end up getting
>> -EAGAIN on request submission. I've dropped it.
>
> I fail to understand without debugging how does it happen, especially since
> it shouldn't even get out of the while in io_wq_submit_work(). Is that
> something obvious I've missed?
I didn't have time to look into it, and haven't yet, just reporting that
it very reliably fails (and under what conditions).
--
Jens Axboe
next prev parent reply other threads:[~2020-12-08 20:23 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-06 22:22 [PATCH 5.10 0/5] iopoll fixes Pavel Begunkov
2020-12-06 22:22 ` [PATCH 5.10 1/5] io_uring: always let io_iopoll_complete() complete polled io Pavel Begunkov
2020-12-07 16:28 ` Jens Axboe
2020-12-08 19:12 ` Pavel Begunkov
2020-12-08 19:17 ` Jens Axboe [this message]
2020-12-08 19:24 ` Pavel Begunkov
2020-12-08 21:10 ` Jens Axboe
2020-12-09 20:17 ` Pavel Begunkov
2020-12-10 17:38 ` Pavel Begunkov
2020-12-06 22:22 ` [PATCH 5.10 2/5] io_uring: fix racy IOPOLL completions Pavel Begunkov
2020-12-07 18:31 ` Pavel Begunkov
2020-12-06 22:22 ` [PATCH 5.10 3/5] io_uring: fix racy IOPOLL flush overflow Pavel Begunkov
2020-12-06 22:22 ` [PATCH 5.10 4/5] io_uring: fix io_cqring_events()'s noflush Pavel Begunkov
2020-12-06 22:22 ` [PATCH 5.10 5/5] io_uring: fix mis-seting personality's creds Pavel Begunkov
2020-12-07 15:05 ` [PATCH 5.10 0/5] iopoll fixes Jens Axboe
2020-12-07 15:24 ` Pavel Begunkov
2020-12-07 15:28 ` Jens Axboe
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