From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Raistlin <raistlin@linux.it>, Ingo Molnar <mingo@elte.hu>,
Thomas Gleixner <tglx@linutronix.de>,
Steven Rostedt <rostedt@goodmis.org>,
Chris Friesen <cfriesen@nortel.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Darren Hart <darren@dvhart.com>,
Johan Eker <johan.eker@ericsson.com>,
"p.faure" <p.faure@akatech.ch>,
linux-kernel <linux-kernel@vger.kernel.org>,
Claudio Scordino <claudio@evidence.eu.com>,
michael trimarchi <trimarchi@retis.sssup.it>,
Fabio Checconi <fabio@gandalf.sssup.it>,
Tommaso Cucinotta <cucinotta@sssup.it>,
Juri Lelli <juri.lelli@gmail.com>,
Nicola Manica <nicola.manica@disi.unitn.it>,
Luca Abeni <luca.abeni@unitn.it>,
Dhaval Giani <dhaval@retis.sssup.it>,
Harald Gustafsson <hgu1972@gmail.com>,
paulmck <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH] sched: Simplify cpu-hot-unplug task migration
Date: Wed, 17 Nov 2010 20:27:13 +0100 [thread overview]
Message-ID: <20101117192713.GA11910@redhat.com> (raw)
In-Reply-To: <1289851597.2109.547.camel@laptop>
Peter, sorry for delay.
I was going to read this patch carefully today, but due to the holiday
in the Czech Republic I have to drink (too much) beer instead ;)
This means you should probably ignore my question, but can't resist...
> -static void migrate_dead_tasks(unsigned int dead_cpu)
> -{
> - struct rq *rq = cpu_rq(dead_cpu);
> - struct task_struct *next;
> + rq->stop = NULL;
(or we could do current->state = TASK_INTERRUPTIPLE, afaics)
> for ( ; ; ) {
> - if (!rq->nr_running)
> + /*
> + * There's this thread running, bail when that's the only
> + * remaining thread.
> + */
> + if (rq->nr_running == 1)
> break;
I was very much confused, and I was going to say this is wrong.
However, now I think this is correct, just the comment is not
right.
There is another running thread we should not migrate, rq->idle.
If nothing else, dequeue_task_idle() should be never called.
But, if I understand correctly, ->nr_running does not account
the idle thread, and this is what makes this correct.
Correct?
Oleg.
next prev parent reply other threads:[~2010-11-17 19:34 UTC|newest]
Thread overview: 135+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-29 6:18 [RFC][PATCH 00/22] sched: SCHED_DEADLINE v3 Raistlin
2010-10-29 6:25 ` [RFC][PATCH 01/22] sched: add sched_class->task_dead Raistlin
2010-10-29 6:27 ` [RFC][PATCH 02/22] sched: add extended scheduling interface Raistlin
2010-11-10 16:00 ` Dhaval Giani
2010-11-10 16:12 ` Dhaval Giani
2010-11-10 22:45 ` Raistlin
2010-11-10 16:17 ` Claudio Scordino
2010-11-10 17:28 ` Peter Zijlstra
2010-11-10 19:26 ` Peter Zijlstra
2010-11-10 23:33 ` Tommaso Cucinotta
2010-11-11 12:19 ` Peter Zijlstra
2010-11-10 22:17 ` Raistlin
2010-11-10 22:57 ` Tommaso Cucinotta
2010-11-11 13:32 ` Peter Zijlstra
2010-11-11 13:54 ` Raistlin
2010-11-11 14:08 ` Peter Zijlstra
2010-11-11 17:27 ` Raistlin
2010-11-11 14:05 ` Dhaval Giani
2010-11-10 22:24 ` Raistlin
2010-11-10 18:50 ` Peter Zijlstra
2010-11-10 22:05 ` Raistlin
2010-11-12 16:38 ` Steven Rostedt
2010-11-12 16:43 ` Peter Zijlstra
2010-11-12 16:52 ` Steven Rostedt
2010-11-12 19:19 ` Raistlin
2010-11-12 19:23 ` Steven Rostedt
2010-11-12 17:42 ` Tommaso Cucinotta
2010-11-12 19:21 ` Steven Rostedt
2010-11-12 19:24 ` Raistlin
2010-10-29 6:28 ` [RFC][PATCH 03/22] sched: SCHED_DEADLINE data structures Raistlin
2010-11-10 18:59 ` Peter Zijlstra
2010-11-10 22:06 ` Raistlin
2010-11-10 19:10 ` Peter Zijlstra
2010-11-12 17:11 ` Steven Rostedt
2010-10-29 6:29 ` [RFC][PATCH 04/22] sched: SCHED_DEADLINE SMP-related " Raistlin
2010-11-10 19:17 ` Peter Zijlstra
2010-10-29 6:30 ` [RFC][PATCH 05/22] sched: SCHED_DEADLINE policy implementation Raistlin
2010-11-10 19:21 ` Peter Zijlstra
2010-11-10 19:43 ` Peter Zijlstra
2010-11-11 1:02 ` Raistlin
2010-11-10 19:45 ` Peter Zijlstra
2010-11-10 22:26 ` Raistlin
2010-11-10 20:21 ` Peter Zijlstra
2010-11-11 1:18 ` Raistlin
2010-11-11 13:13 ` Peter Zijlstra
2010-11-11 14:13 ` Peter Zijlstra
2010-11-11 14:28 ` Raistlin
2010-11-11 14:17 ` Peter Zijlstra
2010-11-11 18:33 ` Raistlin
2010-11-11 14:25 ` Peter Zijlstra
2010-11-11 14:33 ` Raistlin
2010-11-14 8:54 ` Raistlin
2010-11-23 14:24 ` Peter Zijlstra
2010-10-29 6:31 ` [RFC][PATCH 06/22] sched: SCHED_DEADLINE handles spacial kthreads Raistlin
2010-11-11 14:31 ` Peter Zijlstra
2010-11-11 14:50 ` Dario Faggioli
2010-11-11 14:34 ` Peter Zijlstra
2010-11-11 15:27 ` Oleg Nesterov
2010-11-11 15:43 ` Peter Zijlstra
2010-11-11 16:32 ` Oleg Nesterov
2010-11-13 18:35 ` Peter Zijlstra
2010-11-13 19:58 ` Oleg Nesterov
2010-11-13 20:31 ` Peter Zijlstra
2010-11-13 20:51 ` Peter Zijlstra
2010-11-13 23:31 ` Peter Zijlstra
2010-11-15 20:06 ` [PATCH] sched: Simplify cpu-hot-unplug task migration Peter Zijlstra
2010-11-17 19:27 ` Oleg Nesterov [this message]
2010-11-17 19:42 ` Peter Zijlstra
2010-11-18 14:05 ` Oleg Nesterov
2010-11-18 14:24 ` Peter Zijlstra
2010-11-18 15:32 ` Oleg Nesterov
2010-11-18 14:09 ` [tip:sched/core] " tip-bot for Peter Zijlstra
2010-11-11 14:46 ` [RFC][PATCH 06/22] sched: SCHED_DEADLINE handles spacial kthreads Peter Zijlstra
2010-10-29 6:32 ` [RFC][PATCH 07/22] sched: SCHED_DEADLINE push and pull logic Raistlin
2010-11-12 16:17 ` Peter Zijlstra
2010-11-12 21:11 ` Raistlin
2010-11-14 9:14 ` Raistlin
2010-11-23 14:27 ` Peter Zijlstra
2010-10-29 6:33 ` [RFC][PATCH 08/22] sched: SCHED_DEADLINE avg_update accounting Raistlin
2010-11-11 19:16 ` Peter Zijlstra
2010-10-29 6:34 ` [RFC][PATCH 09/22] sched: add period support for -deadline tasks Raistlin
2010-11-11 19:17 ` Peter Zijlstra
2010-11-11 19:31 ` Raistlin
2010-11-11 19:43 ` Peter Zijlstra
2010-11-11 23:33 ` Tommaso Cucinotta
2010-11-12 13:33 ` Raistlin
2010-11-12 13:45 ` Peter Zijlstra
2010-11-12 13:46 ` Luca Abeni
2010-11-12 14:01 ` Raistlin
2010-10-29 6:35 ` [RFC][PATCH 10/22] sched: add a syscall to wait for the next instance Raistlin
2010-11-11 19:21 ` Peter Zijlstra
2010-11-11 19:33 ` Raistlin
2010-10-29 6:35 ` [RFC][PATCH 11/22] sched: add schedstats for -deadline tasks Raistlin
2010-10-29 6:36 ` [RFC][PATCH 12/22] sched: add runtime reporting " Raistlin
2010-11-11 19:37 ` Peter Zijlstra
2010-11-12 16:15 ` Raistlin
2010-11-12 16:27 ` Peter Zijlstra
2010-11-12 21:12 ` Raistlin
2010-10-29 6:37 ` [RFC][PATCH 13/22] sched: add resource limits " Raistlin
2010-11-11 19:57 ` Peter Zijlstra
2010-11-12 21:30 ` Raistlin
2010-11-12 23:32 ` Peter Zijlstra
2010-10-29 6:38 ` [RFC][PATCH 14/22] sched: add latency tracing " Raistlin
2010-10-29 6:38 ` [RFC][PATCH 15/22] sched: add traceporints " Raistlin
2010-11-11 19:54 ` Peter Zijlstra
2010-11-12 16:13 ` Raistlin
2010-10-29 6:39 ` [RFC][PATCH 16/22] sched: add SMP " Raistlin
2010-10-29 6:40 ` [RFC][PATCH 17/22] sched: add signaling overrunning " Raistlin
2010-11-11 21:58 ` Peter Zijlstra
2010-11-12 15:39 ` Raistlin
2010-11-12 16:04 ` Peter Zijlstra
2010-10-29 6:42 ` [RFC][PATCH 19/22] rtmutex: turn the plist into an rb-tree Raistlin
2010-10-29 6:42 ` [RFC][PATCH 18/22] sched: add reclaiming logic to -deadline tasks Raistlin
2010-11-11 22:12 ` Peter Zijlstra
2010-11-12 15:36 ` Raistlin
2010-11-12 16:04 ` Peter Zijlstra
2010-11-12 17:41 ` Luca Abeni
2010-11-12 17:51 ` Peter Zijlstra
2010-11-12 17:54 ` Luca Abeni
2010-11-13 21:08 ` Raistlin
2010-11-12 18:07 ` Tommaso Cucinotta
2010-11-12 19:07 ` Raistlin
2010-11-13 0:43 ` Peter Zijlstra
2010-11-13 1:49 ` Tommaso Cucinotta
2010-11-12 18:56 ` Raistlin
[not found] ` <80992760-24F2-42AE-AF2D-15727F6A1C81@email.unc.edu>
2010-11-15 18:37 ` James H. Anderson
2010-11-15 19:23 ` Luca Abeni
2010-11-15 19:49 ` James H. Anderson
2010-11-15 19:39 ` Luca Abeni
2010-11-15 21:34 ` Raistlin
2010-10-29 6:43 ` [RFC][PATCH 20/22] sched: drafted deadline inheritance logic Raistlin
2010-11-11 22:15 ` Peter Zijlstra
2010-11-14 12:00 ` Raistlin
2010-10-29 6:44 ` [RFC][PATCH 21/22] sched: add bandwidth management for sched_dl Raistlin
2010-10-29 6:45 ` [RFC][PATCH 22/22] sched: add sched_dl documentation Raistlin
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