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From: Jens Axboe <axboe@kernel.dk>
To: Pavel Begunkov <asml.silence@gmail.com>, io-uring@vger.kernel.org
Subject: Re: [PATCHSET 0/3] io_uring: make POLL_ADD support multiple waitqs
Date: Tue, 11 Feb 2020 13:06:00 -0700
Message-ID: <692a561c-9176-63fa-3c48-7f37a8214057@kernel.dk> (raw)
In-Reply-To: <c3fd3aa0-4358-6148-7486-ea52b410a5a6@gmail.com>

On 2/11/20 1:01 PM, Pavel Begunkov wrote:
> On 10/02/2020 23:56, Jens Axboe wrote:
>> As mentioned in the previous email, here are the three patches that add
>> support for multiple waitqueues for polling with io_uring.
>>
>> Patches 1-2 are just basic prep patches, and should not have any
>> functional changes in them. Patch 3 adds support for allocating a new
>> io_poll_iocb unit if we get multiple additions through our queue proc
>> for the wait queues. This new 'poll' addition is queued up as well, and
>> it grabs a reference to the original poll request.
>>
>> Please do review, would love to get this (long standing) issue fixed as
>> it's a real problem for various folks.
>>
> 
> I need to dig a bit deeper into poll to understand some moments, but there is a
> question: don't we won't to support arbitrary number of waitqueues then?

In theory, probably. But in practice, don't think anything exists with > 2
waitqueues. As mentioned, even the 2 waitqueue case is limited to less than
a handful of users.

But the patch should for sure check this, and -EINVAL if we get a third
entry attempted.

-- 
Jens Axboe


      reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-10 20:56 Jens Axboe
2020-02-10 20:56 ` [PATCH 1/3] io_uring: store io_kiocb in wait->private Jens Axboe
2020-02-10 20:56 ` [PATCH 2/3] io_uring: abstract out main poll wake handler Jens Axboe
2020-02-10 20:56 ` [PATCH 3/3] io_uring: allow POLL_ADD with double poll_wait() users Jens Axboe
2020-02-11 20:22   ` Pavel Begunkov
2020-02-11 20:27     ` Jens Axboe
2020-02-11 20:01 ` [PATCHSET 0/3] io_uring: make POLL_ADD support multiple waitqs Pavel Begunkov
2020-02-11 20:06   ` Jens Axboe [this message]

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