From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: umgwanakikbuti@gmail.com, mingo@elte.hu, ktkhai@parallels.com,
rostedt@goodmis.org, tglx@linutronix.de, juri.lelli@gmail.com,
pang.xunlei@linaro.org, wanpeng.li@linux.intel.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 08/14] hrtimer: Allow hrtimer::function() to free the timer
Date: Mon, 8 Jun 2015 00:56:38 +0200 [thread overview]
Message-ID: <20150607225638.GA9329@redhat.com> (raw)
In-Reply-To: <20150607223317.GA5193@redhat.com>
On 06/08, Oleg Nesterov wrote:
>
> And I simply can not understand the complication in hrtimer_active(),
> please help!
Sorry for another off-topic email, but I don't even understand the
usage of hrtimer_active().
Say, do_nanosleep()
hrtimer_start_expires(&t->timer, mode);
if (!hrtimer_active(&t->timer))
t->task = NULL;
why? Assuming that hrtimer_active() is correct, it can only return
false if t->task was already cleared by hrtimer_wakeup().
OTOH. perf_cpu_hrtimer_restart() does
if (hrtimer_active(hr))
return;
if (!hrtimer_callback_running(hr))
__hrtimer_start_range_ns(...);
why it can't simply do
if (!hrtimer_active(hr)) // implies !hrtimer_callback_running()
__hrtimer_start_range_ns(...);
Confused.
Oleg.
next prev parent reply other threads:[~2015-06-07 22:57 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-05 8:48 [PATCH 00/14] sched: balance callbacks Peter Zijlstra
2015-06-05 8:48 ` [PATCH 01/14] sched: Replace post_schedule with a balance callback list Peter Zijlstra
2015-06-05 8:48 ` [PATCH 02/14] sched: Use replace normalize_task() with __sched_setscheduler() Peter Zijlstra
2015-06-05 8:48 ` [PATCH 03/14] sched: Allow balance callbacks for check_class_changed() Peter Zijlstra
2015-06-05 8:48 ` [PATCH 04/14] sched,rt: Remove return value from pull_rt_task() Peter Zijlstra
2015-06-05 8:48 ` [PATCH 05/14] sched,rt: Convert switched_{from,to}_rt() / prio_changed_rt() to balance callbacks Peter Zijlstra
2015-06-05 8:48 ` [PATCH 06/14] sched,dl: Remove return value from pull_dl_task() Peter Zijlstra
2015-06-05 8:48 ` [PATCH 07/14] sched,dl: Convert switched_{from,to}_dl() / prio_changed_dl() to balance callbacks Peter Zijlstra
2015-06-05 8:48 ` [PATCH 08/14] hrtimer: Allow hrtimer::function() to free the timer Peter Zijlstra
2015-06-05 9:48 ` Thomas Gleixner
2015-06-07 19:43 ` Oleg Nesterov
2015-06-07 22:33 ` Oleg Nesterov
2015-06-07 22:56 ` Oleg Nesterov [this message]
2015-06-08 8:06 ` Thomas Gleixner
2015-06-08 9:14 ` Peter Zijlstra
2015-06-08 10:55 ` Peter Zijlstra
2015-06-08 12:42 ` Peter Zijlstra
2015-06-08 14:27 ` Oleg Nesterov
2015-06-08 14:42 ` Peter Zijlstra
2015-06-08 15:49 ` Oleg Nesterov
2015-06-08 15:10 ` Peter Zijlstra
2015-06-08 15:16 ` Oleg Nesterov
2015-06-09 21:33 ` Oleg Nesterov
2015-06-09 21:39 ` Oleg Nesterov
2015-06-10 6:55 ` Peter Zijlstra
2015-06-10 7:46 ` Kirill Tkhai
2015-06-10 16:04 ` Oleg Nesterov
2015-06-11 7:31 ` Peter Zijlstra
2015-06-11 16:25 ` Kirill Tkhai
2015-06-10 15:49 ` Oleg Nesterov
2015-06-10 22:37 ` Peter Zijlstra
2015-06-08 14:03 ` Oleg Nesterov
2015-06-08 14:17 ` Peter Zijlstra
2015-06-08 15:10 ` [PATCH 0/3] hrtimer: HRTIMER_STATE_ fixes Oleg Nesterov
2015-06-08 15:11 ` [PATCH 2/3] hrtimer: turn newstate arg of __remove_hrtimer() into clear_enqueued Oleg Nesterov
2015-06-08 15:11 ` [PATCH 3/3] hrtimer: fix the __hrtimer_start_range_ns() race with hrtimer_active() Oleg Nesterov
2015-06-08 15:12 ` [PATCH 1/3] hrtimer: kill HRTIMER_STATE_MIGRATE, fix the race with hrtimer_is_queued() Oleg Nesterov
2015-06-08 15:35 ` [PATCH 0/3] hrtimer: HRTIMER_STATE_ fixes Peter Zijlstra
2015-06-08 15:56 ` Oleg Nesterov
2015-06-08 17:11 ` Thomas Gleixner
2015-06-08 19:08 ` Peter Zijlstra
2015-06-08 20:52 ` Oleg Nesterov
2015-06-08 15:10 ` [PATCH 1/3] hrtimer: kill HRTIMER_STATE_MIGRATE, fix the race with hrtimer_is_queued() Oleg Nesterov
2015-06-08 15:13 ` Oleg Nesterov
2015-06-05 8:48 ` [PATCH 09/14] sched,dl: Fix sched class hopping CBS hole Peter Zijlstra
2015-06-05 8:48 ` [PATCH 10/14] sched: Move code around Peter Zijlstra
2015-06-05 8:48 ` [PATCH 11/14] sched: Streamline the task migration locking a little Peter Zijlstra
2015-06-05 8:48 ` [PATCH 12/14] lockdep: Simplify lock_release() Peter Zijlstra
2015-06-05 8:48 ` [PATCH 13/14] lockdep: Implement lock pinning Peter Zijlstra
2015-06-05 9:55 ` Ingo Molnar
2015-06-11 11:37 ` Peter Zijlstra
2015-06-05 8:48 ` [PATCH 14/14] sched,lockdep: Employ " Peter Zijlstra
2015-06-05 9:57 ` Ingo Molnar
2015-06-05 11:03 ` Peter Zijlstra
2015-06-05 11:24 ` Ingo Molnar
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