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From: Tejun Heo <tj@kernel.org>
To: Waiman Long <longman@redhat.com>
Cc: Li Zefan <lizefan@huawei.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
	kernel-team@fb.com, pjt@google.com, luto@amacapital.net,
	efault@gmx.de, torvalds@linux-foundation.org, guro@fb.com
Subject: Re: [PATCH] cgroup: remove unnecessary empty check when enabling threaded mode
Date: Tue, 25 Jul 2017 13:16:08 -0400	[thread overview]
Message-ID: <20170725171607.GC3216015@devbig577.frc2.facebook.com> (raw)
In-Reply-To: <20170723121826.GC1498614@devbig577.frc2.facebook.com>

On Sun, Jul 23, 2017 at 08:18:26AM -0400, Tejun Heo wrote:
> cgroup_enable_threaded() checks that the cgroup doesn't have any tasks
> or children and fails the operation if so.  This test is unnecessary
> because the first part is already checked by
> cgroup_can_be_thread_root() and the latter is unnecessary.  The latter
> actually cause a behavioral oddity.  Please consider the following
> hierarchy.  All cgroups are domains.
> 
>     A
>    / \
>   B   C
>        \
>         D
> 
> If B is made threaded, C and D becomes invalid domains.  Due to the no
> children restriction, threaded mode can't be enabled on C.  For C and
> D, the only thing the user can do is removal.
> 
> There is no reason for this restriction.  Remove it.
> 
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Cc: Waiman Long <longman@redhat.com>

Applied to cgroup/for-4.14 with Waiman's ack.

Thanks.

-- 
tejun

  parent reply	other threads:[~2017-07-25 17:16 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-07-21 20:34 [PATCH v2 0/4] cgroup: Introducing bypass mode Waiman Long
2017-07-21 20:34 ` Waiman Long
     [not found] ` <1500669293-21792-1-git-send-email-longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-07-21 20:34   ` [PATCH v2 1/4] cgroup: Child cgroup creation not allowed on invalid domain Waiman Long
2017-07-21 20:34     ` Waiman Long
2017-07-22 13:43     ` Tejun Heo
     [not found]       ` <20170722134358.GB3329631-4dN5La/x3IkLX0oZNxdnEQ2O0Ztt9esIQQ4Iyu8u01E@public.gmane.org>
2017-07-23 12:18         ` [PATCH] cgroup: remove unnecessary empty check when enabling threaded mode Tejun Heo
2017-07-23 12:18           ` Tejun Heo
     [not found]           ` <20170723121826.GC1498614-4dN5La/x3IkLX0oZNxdnEQ2O0Ztt9esIQQ4Iyu8u01E@public.gmane.org>
2017-07-24 19:14             ` Waiman Long
2017-07-24 19:14               ` Waiman Long
     [not found]               ` <c2637f47-3e90-a322-f84b-0c913da14977-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-07-25 17:22                 ` [PATCH cgroup/for-4.14] cgroup: add comment to cgroup_enable_threaded() Tejun Heo
2017-07-25 17:22                   ` Tejun Heo
2017-07-25 17:16           ` Tejun Heo [this message]
2017-07-24 17:48       ` [PATCH v2 1/4] cgroup: Child cgroup creation not allowed on invalid domain Waiman Long
2017-07-21 20:34 ` [PATCH v2 2/4] cgroup: Allow bypass mode in subtree_control Waiman Long
     [not found]   ` <1500669293-21792-3-git-send-email-longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-07-22 13:50     ` Tejun Heo
2017-07-22 13:50       ` Tejun Heo
     [not found]       ` <20170722135030.GC3329631-4dN5La/x3IkLX0oZNxdnEQ2O0Ztt9esIQQ4Iyu8u01E@public.gmane.org>
2017-07-24 18:20         ` Waiman Long
2017-07-24 18:20           ` Waiman Long
2017-07-25 17:13           ` Tejun Heo
     [not found]             ` <20170725171343.GB3216015-4dN5La/x3IkLX0oZNxdnEQ2O0Ztt9esIQQ4Iyu8u01E@public.gmane.org>
2017-07-25 19:10               ` Waiman Long
2017-07-25 19:10                 ` Waiman Long
2017-08-01 14:29             ` Waiman Long
2017-07-21 20:34 ` [PATCH v2 3/4] cgroup: Allow reenabling of controller in bypass mode Waiman Long
2017-07-21 20:34 ` [PATCH v2 4/4] cgroup: Make debug controller report new controller masks Waiman Long

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