From: Jens Axboe <[email protected]>
To: Andres Freund <[email protected]>
Cc: [email protected]
Subject: Re: [PATCH 5/6] io_uring: add support for futex wake and wait
Date: Fri, 23 Jun 2023 13:07:12 -0600 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 6/23/23 1:04?PM, Andres Freund wrote:
> Hi,
>
> I'd been chatting with Jens about this, so obviously I'm interested in the
> feature...
>
> On 2023-06-09 12:31:24 -0600, Jens Axboe wrote:
>> Add support for FUTEX_WAKE/WAIT primitives.
>>
>> IORING_OP_FUTEX_WAKE is mix of FUTEX_WAKE and FUTEX_WAKE_BITSET, as
>> it does support passing in a bitset.
>>
>> Similary, IORING_OP_FUTEX_WAIT is a mix of FUTEX_WAIT and
>> FUTEX_WAIT_BITSET.
>
> One thing I was wondering about is what happens when there are multiple
> OP_FUTEX_WAITs queued for the same futex, and that futex gets woken up. I
> don't really have an opinion about what would be best, just that it'd be
> helpful to specify the behaviour.
Not sure I follow the question, can you elaborate?
If you have N futex waits on the same futex and someone does a wait
(with wakenum >= N), then they'd all wake and post a CQE. If less are
woken because the caller asked for less than N, than that number should
be woken.
IOW, should have the same semantics as "normal" futex waits.
Or maybe I'm totally missing what is being asked here...
--
Jens Axboe
next prev parent reply other threads:[~2023-06-23 19:07 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-09 18:31 [PATCHSET RFC 0/6] Add io_uring support for futex wait/wake Jens Axboe
2023-06-09 18:31 ` [PATCH 1/6] futex: abstract out futex_op_to_flags() helper Jens Axboe
2023-06-09 18:31 ` [PATCH 2/6] futex: factor out the futex wake handling Jens Axboe
2023-06-09 18:31 ` [PATCH 3/6] futex: assign default futex_q->wait_data at insertion time Jens Axboe
2023-06-09 18:31 ` [PATCH 4/6] futex: add futex wait variant that takes a futex_q directly Jens Axboe
2023-06-09 18:31 ` [PATCH 5/6] io_uring: add support for futex wake and wait Jens Axboe
2023-06-12 16:06 ` Gabriel Krisman Bertazi
2023-06-12 20:37 ` Jens Axboe
2023-06-12 23:00 ` Gabriel Krisman Bertazi
2023-06-13 1:09 ` Jens Axboe
2023-06-13 2:55 ` io_uring link semantics (was [PATCH 5/6] io_uring: add support for futex wake and wait) Gabriel Krisman Bertazi
2023-06-23 19:04 ` [PATCH 5/6] io_uring: add support for futex wake and wait Andres Freund
2023-06-23 19:07 ` Jens Axboe [this message]
2023-06-23 19:34 ` Andres Freund
2023-06-23 19:46 ` Jens Axboe
2023-06-09 18:31 ` [PATCH 6/6] io_uring/futex: enable use of the allocation caches for futex_q Jens Axboe
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