Re: [Qemu-devel] [PATCH v3 01/10] Introduce qemu_cond_timedwait for POSIX

[malc]

On Thu, 5 Apr 2012, Jan Kiszka wrote:

> On 2012-04-05 15:00, malc wrote:
> > On Thu, 5 Apr 2012, Jan Kiszka wrote:
> > 
> >> On 2012-04-05 14:56, Paolo Bonzini wrote:
> >>> Il 05/04/2012 14:53, malc ha scritto:
> >>>> On Thu, 5 Apr 2012, Paolo Bonzini wrote:
> >>>>
> >>>>> Il 05/04/2012 14:30, malc ha scritto:
> >>>>>>>> Would save that "* 1000". I just wondered why we do not use it 
> >>>>>>>> elsewhere
> >>>>>>>> in QEMU and was reluctant to risk some BSD breakage.
> >>>>>>>>
> >>>>>> It's probably worth mentioning that using anything other than 
> >>>>>> clock_gettime and CLOCK_MONOTONING (as well as setting proper pthread
> >>>>>> clock attr on the condition variable) is prone to the surprises (such
> >>>>>> as NTP corrections and daylight saving changes).
> >>>>>
> >>>>> I was about to suggest the same, but how widespread is support for
> >>>>> pthread_condattr_setclock?
> >>>>
> >>>> If it's not all is lost anyway.
> >>>
> >>> Only once every year. :)
> >>
> >> ...and not for the current user of this service which do not care that
> >> much about the timeout and a potential delay or early shot.
> >>
> > 
> > An hour of potential delay mind you.
> 
> Nope, look at posix-aio-compat. It's an optimization to keep the number
> worker threads under control.

The code attempts to sleep for ten seconds, which can turn into an hour
and ten seconds if the conditions are right.

> 
> Granted, time adjustments can make qemu_cond_timedwait in this primitive
> (but easily portable) form less useful for other purposes.
> 
> Jan
> 
> 

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