linux-kernel - Re: [PATCH v2] sched: fix first task of a task group is attached twice

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Date:	Thu, 26 May 2016 10:26:54 +0200
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Yuyang Du <yuyang.du@...el.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>
Subject: Re: [PATCH v2] sched: fix first task of a task group is attached twice

On 26 May 2016 at 00:38, Yuyang Du <yuyang.du@...el.com> wrote:
> On Wed, May 25, 2016 at 05:01:11PM +0200, Vincent Guittot wrote:
>> The cfs_rq->avg.last_update_time is initialize to 0 with the main effect
>> that the 1st sched_entity that will be attached, will keep its
>> last_update_time set to 0 and will attached once again during the
>> enqueue.
>> Initialize cfs_rq->avg.last_update_time to 1 instead.
>
> Actually, the first time (attach_task_cfs_rq()) is called even way
> before init_entity_runnable_average(), no?

maybe there is an issue during the fork of a task too
This patch is about the init of the sched_avg of a task group. The
problem happens when the 1st task is moved the group but it's not
about the fork of a task