From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Yong Zhang <yong.zhang0@gmail.com>,
Chris Mason <chris.mason@oracle.com>,
Frank Rowand <frank.rowand@am.sony.com>,
Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
Mike Galbraith <efault@gmx.de>, Paul Turner <pjt@google.com>,
Jens Axboe <axboe@kernel.dk>,
Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH 08/17] sched: Drop the rq argument to sched_class::select_task_rq()
Date: Mon, 03 Jan 2011 17:41:36 +0100 [thread overview]
Message-ID: <1294072896.2016.103.camel@laptop> (raw)
In-Reply-To: <1294072517.2016.101.camel@laptop>
On Mon, 2011-01-03 at 17:35 +0100, Peter Zijlstra wrote:
> > In fact, I am completely confused. I do not understand why do we
> > check task_running() at all. If we see on_rq == 0 && on_cpu == 1,
> > then this task is going to clear its on_cpu soon, once it finishes
> > context_switch().
>
> > Probably, this check was needed before, try_to_wake_up() could
> > activate the task_running() task without migrating. But, at first
> > glance, this is no longer possible after this series?
>
> It can still do that, I think the problem is us dropping rq->lock in the
> middle of schedule(), when the freshly woken migration thread comes in
> between there and moves the task away, you can get into the situation
> that two cpus reference the same task_struct at the same time, which
> usually leads to 'interesting' situations.
Frr, brainfart, you cannot schedule the migration thread without
completely finishing prev.
/me goes ponder more
next prev parent reply other threads:[~2011-01-03 16:41 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-24 12:23 [RFC][PATCH 00/17] sched: Reduce runqueue lock contention -v3 Peter Zijlstra
2010-12-24 12:23 ` [RFC][PATCH 01/17] sched: Always provide p->on_cpu Peter Zijlstra
2010-12-24 12:23 ` [RFC][PATCH 02/17] mutex: Use p->on_cpu for the adaptive spin Peter Zijlstra
2010-12-24 12:23 ` [RFC][PATCH 03/17] sched: Change the ttwu success details Peter Zijlstra
2010-12-24 12:23 ` [RFC][PATCH 04/17] sched: Clean up ttwu stats Peter Zijlstra
2010-12-24 12:23 ` [RFC][PATCH 05/17] x86: Optimize arch_spin_unlock_wait() Peter Zijlstra
2010-12-24 18:26 ` Linus Torvalds
2011-01-03 11:32 ` Peter Zijlstra
2011-01-04 6:45 ` Nick Piggin
2011-01-05 19:14 ` [RFC][PATCH] spinlock: Kill spin_unlock_wait() Peter Zijlstra
2011-01-05 19:26 ` Oleg Nesterov
2011-01-05 19:43 ` Linus Torvalds
2011-01-06 9:32 ` Peter Zijlstra
2011-01-06 10:38 ` Nick Piggin
2011-01-06 18:26 ` Peter Zijlstra
2011-01-07 21:01 ` Tejun Heo
2011-01-07 21:13 ` Jeff Garzik
2011-01-07 21:33 ` Tejun Heo
2010-12-24 12:23 ` [RFC][PATCH 06/17] sched: Provide p->on_rq Peter Zijlstra
2010-12-29 14:14 ` Yong Zhang
2010-12-24 12:23 ` [RFC][PATCH 07/17] sched: Serialize p->cpus_allowed and ttwu() using p->pi_lock Peter Zijlstra
2010-12-29 14:20 ` Yong Zhang
2011-01-03 11:12 ` Peter Zijlstra
2010-12-24 12:23 ` [RFC][PATCH 08/17] sched: Drop the rq argument to sched_class::select_task_rq() Peter Zijlstra
2010-12-29 14:31 ` Yong Zhang
2011-01-03 11:16 ` Peter Zijlstra
2011-01-03 14:59 ` Oleg Nesterov
2011-01-03 15:21 ` Peter Zijlstra
2011-01-03 15:49 ` Oleg Nesterov
2011-01-03 16:35 ` Peter Zijlstra
2011-01-03 16:41 ` Peter Zijlstra [this message]
2011-01-04 7:27 ` Yong Zhang
2011-01-04 12:34 ` Peter Zijlstra
2011-01-04 5:59 ` Yong Zhang
2011-01-04 13:00 ` Peter Zijlstra
2011-01-03 18:05 ` Oleg Nesterov
2011-01-04 13:01 ` Peter Zijlstra
2010-12-24 12:23 ` [RFC][PATCH 09/17] sched: Remove rq argument to sched_class::task_waking() Peter Zijlstra
2010-12-24 12:23 ` [RFC][PATCH 10/17] sched: Add TASK_WAKING to task_rq_lock Peter Zijlstra
2010-12-24 12:23 ` [RFC][PATCH 11/17] sched: Delay task_contributes_to_load() Peter Zijlstra
2010-12-24 12:23 ` [RFC][PATCH 12/17] sched: Also serialize ttwu_local() with p->pi_lock Peter Zijlstra
2011-01-03 17:32 ` Oleg Nesterov
2011-01-09 23:11 ` Tejun Heo
2010-12-24 12:23 ` [RFC][PATCH 13/17] sched: Remove rq->lock from the first half of ttwu() Peter Zijlstra
2010-12-24 12:23 ` [RFC][PATCH 14/17] sched: Remove rq argument to ttwu_stat() Peter Zijlstra
2010-12-29 14:40 ` Yong Zhang
2011-01-03 11:20 ` Peter Zijlstra
2010-12-24 12:23 ` [RFC][PATCH 15/17] sched: Rename ttwu_post_activation Peter Zijlstra
2010-12-24 12:23 ` [RFC][PATCH 16/17] sched: Move the second half of ttwu() to the remote cpu Peter Zijlstra
2011-01-03 14:36 ` [RFC][PATCH] sembench: add stddev to the burn stats Peter Zijlstra
2011-01-04 14:28 ` [RFC][PATCH 16/17] sched: Move the second half of ttwu() to the remote cpu Oleg Nesterov
2011-01-04 14:47 ` Peter Zijlstra
2011-01-04 15:18 ` Oleg Nesterov
2011-01-04 15:43 ` Peter Zijlstra
2011-01-04 16:06 ` Oleg Nesterov
2010-12-24 12:23 ` [RFC][PATCH 17/17] sched: Sort hotplug vs ttwu queueing Peter Zijlstra
2010-12-29 14:51 ` Yong Zhang
2011-01-03 11:21 ` Peter Zijlstra
2010-12-24 13:15 ` [RFC][PATCH 00/17] sched: Reduce runqueue lock contention -v3 Peter Zijlstra
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