Date: Thu, 16 Feb 2012 16:42:34 -0800 From: Julian Elischer <julian@freebsd.org> To: Andriy Gapon <avg@freebsd.org> Cc: Alexander Kabaev <kan@freebsd.org>, threads@freebsd.org, FreeBSD Stable <freebsd-stable@freebsd.org>, David Xu <davidxu@freebsd.org> Subject: Re: pthread_cond_timedwait() broken in 9-stable? (from JAN 10) Message-ID: <4F3DA27A.3090903@freebsd.org> In-Reply-To: <4F3D89CD.9050309@freebsd.org> References: <4F3C2671.3090808__7697.00510795719$1329343207$gmane$org@freebsd.org> <4F3D3E2D.9090100@FreeBSD.org> <4F3D6FDD.9050808@freebsd.org> <4F3D89CD.9050309@freebsd.org>
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Adding David Xu for his thoughts since he reqrote the code in quesiton in revision 213098 On 2/16/12 2:57 PM, Julian Elischer wrote: > On 2/16/12 1:06 PM, Julian Elischer wrote: >> On 2/16/12 9:34 AM, Andriy Gapon wrote: >>> on 15/02/2012 23:41 Julian Elischer said the following: >>>> The program fio (an IO test in ports) uses pthreads >>>> >>>> the following code (from fio-2.0.3, but its in earlier code too) >>>> has suddenly started misbehaving. >>>> >>>> clock_gettime(CLOCK_REALTIME,&t); >>>> t.tv_sec += seconds + 10; >>>> >>>> pthread_mutex_lock(&mutex->lock); >>>> >>>> while (!mutex->value&& !ret) { >>>> mutex->waiters++; >>>> ret = >>>> pthread_cond_timedwait(&mutex->cond,&mutex->lock,&t); >>>> mutex->waiters--; >>>> } >>>> >>>> if (!ret) { >>>> mutex->value--; >>>> pthread_mutex_unlock(&mutex->lock); >>>> } >>>> >>>> >>>> It turns out that 'ret' sometimes comes back instantly (on my >>>> machine) with a >>>> value of 60 (ETIMEDOUT) >>>> despite the fact that we set the timeout 10 seconds into the future. >>>> >>>> Has anyone else seen anything like this? >>>> (and yes the condition variable attribute have been set to use >>>> the REALTIME clock). >>> But why? >>> >>> Just a hypothesis that maybe there is some issue with time keeping >>> on that system. >>> How would that code work out for you with MONOTONIC? >> >> Jens Axboe, (CC'd) tried both CLOCK_REALTIME and CLOCK_MONOTONIC, >> and they both had the same problem.. >> i.e. random early returns with ETIMEDOUT. >> >> I think we will try move out machine forward to a newer -stable to >> see if it resolves. > Kan upgraded the machine today to today's 9.x branch tip and the > problem still occurs. > 8.x does not have this problem. > > I have not got a 9-RELEASE machine to test on.. so I can not tell if > this came in with the burst of stuff > that came in after the 9.x branch was unfrozen after the release of > 9.0. > >
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