From: Kirill Tkhai <tkhai@yandex.ru>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>,
Michael wang <wangyun@linux.vnet.ibm.com>,
"ktkhai@parallels.com" <ktkhai@parallels.com>,
Ingo Molnar <mingo@kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: sched: hang in migrate_swap
Date: Wed, 14 May 2014 14:21:04 +0400 [thread overview]
Message-ID: <2158101400062864@web10h.yandex.ru> (raw)
In-Reply-To: <20140514101354.GI30445@twins.programming.kicks-ass.net>
14.05.2014, 14:14, "Peter Zijlstra" <peterz@infradead.org>:
> On Wed, May 14, 2014 at 01:42:32PM +0400, Kirill Tkhai wrote:
>
>> Peter, do we have to queue stop works orderly?
>>
>> Is there is not a possibility, when two pair of works queued different on
>> different cpus?
>>
>> kernel/stop_machine.c | 10 ++++++++--
>> 1 file changed, 8 insertions(+), 2 deletions(-)
>> diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
>> index b6b67ec..29e221b 100644
>> --- a/kernel/stop_machine.c
>> +++ b/kernel/stop_machine.c
>> @@ -250,8 +250,14 @@ struct irq_cpu_stop_queue_work_info {
>> static void irq_cpu_stop_queue_work(void *arg)
>> {
>> struct irq_cpu_stop_queue_work_info *info = arg;
>> - cpu_stop_queue_work(info->cpu1, info->work1);
>> - cpu_stop_queue_work(info->cpu2, info->work2);
>> +
>> + if (info->cpu1 < info->cpu2) {
>> + cpu_stop_queue_work(info->cpu1, info->work1);
>> + cpu_stop_queue_work(info->cpu2, info->work2);
>> + } else {
>> + cpu_stop_queue_work(info->cpu2, info->work2);
>> + cpu_stop_queue_work(info->cpu1, info->work1);
>> + }
>> }
>
> I'm not sure, we already send the IPI to the first cpu of the pair, so
> supposing we have 4 cpus, and get 4 pairs like:
>
> 0,1 1,2 2,3 3,0
>
> That would result in IPIs to 0, 1, 2, and 0 again, and since the IPI
> function is serialized I don't immediately see a way for this to
> deadlock.
It's about stop_two_cpus(), I have a distrust about other users of stop task:
queue_stop_cpus_work() queues work consequentially:
0 1 2 4
stop_two_cpus() may queue:
1 0
Looks like, stop thread on 0th and on 1th are waiting for wrong works.
next prev parent reply other threads:[~2014-05-14 10:21 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-19 18:08 sched: hang in migrate_swap Sasha Levin
2014-02-20 4:32 ` Michael wang
2014-02-21 16:43 ` Sasha Levin
2014-02-22 1:45 ` Michael wang
2014-02-24 3:23 ` Sasha Levin
2014-02-24 5:19 ` Michael wang
2014-02-24 5:54 ` Sasha Levin
2014-02-24 7:10 ` Peter Zijlstra
2014-02-24 10:14 ` Michael wang
2014-02-24 12:12 ` Peter Zijlstra
2014-02-24 13:10 ` Peter Zijlstra
2014-02-25 4:47 ` Michael wang
2014-02-25 10:49 ` Peter Zijlstra
2014-02-26 2:32 ` Michael wang
2014-02-24 18:21 ` Sasha Levin
2014-02-25 2:48 ` Michael wang
2014-02-25 11:03 ` Peter Zijlstra
2014-02-25 3:01 ` Michael wang
2014-02-27 13:33 ` [tip:sched/core] sched: Guarantee task priority in pick_next_task () tip-bot for Peter Zijlstra
2014-04-10 3:31 ` sched: hang in migrate_swap Sasha Levin
2014-04-10 6:59 ` Michael wang
2014-04-10 13:38 ` Kirill Tkhai
2014-04-11 14:32 ` Sasha Levin
2014-04-11 15:16 ` Kirill Tkhai
2014-05-12 18:48 ` Sasha Levin
2014-05-14 9:42 ` Kirill Tkhai
2014-05-14 10:13 ` Peter Zijlstra
2014-05-14 10:21 ` Kirill Tkhai [this message]
2014-05-14 10:26 ` Peter Zijlstra
2014-05-14 11:20 ` Peter Zijlstra
2015-06-15 19:38 ` Rafael David Tinoco
2015-06-15 19:47 ` Peter Zijlstra
2014-04-18 8:24 ` [tip:sched/urgent] sched: Check for stop task appearance when balancing happens tip-bot for Kirill Tkhai
2014-04-10 7:42 ` sched: hang in migrate_swap Peter Zijlstra
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