From: Frederic Weisbecker <fweisbec@gmail.com>
To: kosaki.motohiro@gmail.com
Cc: linux-kernel@vger.kernel.org,
Olivier Langlois <olivier@trillion01.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: [PATCH 2/7] posix-cpu-timers: fix acounting delta_exec twice
Date: Sat, 11 May 2013 02:56:14 +0200 [thread overview]
Message-ID: <20130511005613.GC13340@somewhere> (raw)
In-Reply-To: <1367556468-4021-4-git-send-email-kosaki.motohiro@gmail.com>
On Fri, May 03, 2013 at 12:47:43AM -0400, kosaki.motohiro@gmail.com wrote:
> From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>
> Currently glibc rt/tst-cpuclock2 test(*) sporadically fails because
> scheduler delta can be accounted twice from thread_group_cputimer()
> and account_group_exec_runtime().
>
> Finally, clock_nanosleep() wakes up before an argument. This is posix
> violation. This issue was introduced by commit d670ec1317 (posix-cpu-timers:
> Cure SMP wobbles).
>
> (*) http://sourceware.org/git/?p=glibc.git;a=blob;f=rt/tst-cpuclock2.c;h=6752721717f959e89c0d692b3f1ee082d507eec2;hb=HEAD
>
> Cc: Olivier Langlois <olivier@trillion01.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Signed-off-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
[...]
> diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
> index 8fd709c..e56be4c 100644
> --- a/kernel/posix-cpu-timers.c
> +++ b/kernel/posix-cpu-timers.c
> @@ -220,7 +220,7 @@ static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
> cpu->cpu = virt_ticks(p);
> break;
> case CPUCLOCK_SCHED:
> - cpu->sched = task_sched_runtime(p);
> + cpu->sched = task_sched_runtime(p, true);
> break;
> }
> return 0;
> @@ -250,8 +250,13 @@ void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
> * values through the TIMER_ABSTIME flag, therefore we have
> * to synchronize the timer to the clock every time we start
> * it.
> + *
> + * Do not add the current delta, because
> + * account_group_exec_runtime() will also this delta and we
> + * wouldn't want to double account time and get ahead of
> + * ourselves.
> */
> - thread_group_cputime(tsk, &sum);
> + thread_group_cputime(tsk, false, &sum);
> raw_spin_lock_irqsave(&cputimer->lock, flags);
I wonder if we should move thread_group_cputime() inside this lock.
Otherwise we can miss some updates in-between.
next prev parent reply other threads:[~2013-05-11 0:56 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-03 4:47 [PATCH v4 0/7] posix timers fixlet kosaki.motohiro
2013-05-03 4:47 ` [PATCH 1/7] posix-cpu-timers: don't account cpu timer after stopped thread runtime accounting kosaki.motohiro
2013-05-06 23:47 ` Frederic Weisbecker
2013-05-07 2:57 ` KOSAKI Motohiro
2013-05-07 15:24 ` Frederic Weisbecker
2013-05-26 21:38 ` KOSAKI Motohiro
2013-05-07 3:16 ` Olivier Langlois
2013-05-11 0:17 ` Frederic Weisbecker
2013-05-11 2:40 ` KOSAKI Motohiro
2013-05-03 4:47 ` [PATCH 2/7] posix-cpu-timers: fix acounting delta_exec twice kosaki.motohiro
2013-05-11 0:56 ` Frederic Weisbecker [this message]
2013-05-11 2:17 ` KOSAKI Motohiro
2013-05-03 4:47 ` [PATCH 3/7] posix-cpu-timers: fix wrong timer initialization kosaki.motohiro
2013-05-03 4:47 ` [PATCH 4/7] posix-cpu-timers: timer functions should use timer time instead of clock time kosaki.motohiro
2013-05-03 4:47 ` [PATCH 5/7] posix-cpu-timers: check_thread_timers() uses task_sched_runtime() kosaki.motohiro
2013-05-03 4:47 ` [PATCH 6/7] sched: task_sched_runtime introduce micro optimization kosaki.motohiro
2013-05-03 4:47 ` [PATCH 7/7] posix-cpu-timers: cleanup cpu_{clock,timer}_sample{,_group} kosaki.motohiro
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