lkml.org 
[lkml]   [2019]   [Dec]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH 1/1] io_uring: don't wait when under-submitting
Date

> On Dec 13, 2019, at 2:32 PM, Pavel Begunkov <asml.silence@gmail.com> wrote:
>
> On 13/12/2019 21:32, Jens Axboe wrote:
>>> On 12/13/19 11:22 AM, Jens Axboe wrote:
>>> On 12/13/19 12:51 AM, Pavel Begunkov wrote:
>>>> There is no reliable way to submit and wait in a single syscall, as
>>>> io_submit_sqes() may under-consume sqes (in case of an early error).
>>>> Then it will wait for not-yet-submitted requests, deadlocking the user
>>>> in most cases.
>>>
>>> Why not just cap the wait_nr? If someone does to_submit = 8, wait_nr = 8,
>>> and we only submit 4, just wait for 4? Ala:
>>>
>
> Is it worth entangling the code? I don't expect anyone trying to recover,
> maybe except full reset/restart. So, failing ASAP seemed to me as the
> right thing to do. It may also mean nothing to the user if e.g.
> submit(1), submit(1), ..., submit_and_wait(1, n)
>
> Anyway, this shouldn't even happen in a not buggy code, so I'm fine with
> any version as long as it doesn't lock up. I'll resend if you still prefer
> to cap it.

I like the cap version a lot better, and in fact we did used to have that but lost it early. I like it behaviorally a lot better, too.

Can you resend? Thanks!

\
 
 \ /
  Last update: 2019-12-13 22:48    [W:0.064 / U:0.272 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site