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List:       git
Subject:    Re: [PATCH] poll/select: prevent busy-waiting
From:       Erik Faye-Lund <kusmabite () gmail ! com>
Date:       2014-04-28 11:44:34
Message-ID: CABPQNSbDkE+Vff=4MmPO9oMfjRay6Oin51zZRoZ8mOEhGoaD3Q () mail ! gmail ! com
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On Mon, Apr 28, 2014 at 1:42 PM, Stepan Kasal <kasal@ucw.cz> wrote:
> From: Paolo Bonzini <bonzini@gnu.org>
> Date: Mon, 21 May 2012 09:52:42 +0200
>
> Backported from Gnulib.
>
> 2012-05-21  Paolo Bonzini  <bonzini@gnu.org>
>
>         poll/select: prevent busy-waiting.  SwitchToThread() only gives away
>         the rest of the current time slice to another thread in the current
>         process. So if the thread that feeds the file decscriptor we're
>         polling is not in the current process, we get busy-waiting.
>         * lib/poll.c: Use SleepEx(1, TRUE) instead of SwitchToThread().
>         Patch from Theodore Leblond.
>         * lib/select.c: Split polling out of the loop that sets the output
>         fd_sets.  Check for zero result and loop if the wait timeout is
>         infinite.
>
> Signed-off-by: Stepan Kasal <kasal@ucw.cz>
> ---
>  compat/poll/poll.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/compat/poll/poll.c b/compat/poll/poll.c
> index 31163f2..a9b41d8 100644
> --- a/compat/poll/poll.c
> +++ b/compat/poll/poll.c
> @@ -605,7 +605,7 @@ restart:
>
>    if (!rc && timeout == INFTIM)
>      {
> -      SwitchToThread();
> +      SleepEx (1, TRUE);
>        goto restart;
>      }
>
> --
> 1.9.2.msysgit.0.158.g6070cee
>

Thanks for taking the effort!

Acked-by: Erik Faye-Lund <kusmabite@gmail.com>
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