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received-spf: None (protection.outlook.com: fb.com does not designate permitted sender hosts) x-microsoft-antispam-message-info: XMKDqAUabn2K6nbg4tfryCfP+d5rS9VdAS0fJOB6G5H4mTwHL0dfgEKEwU/fzDCgbMMdDNCS91SbdCPm2tdufIbK4WfNPnSVuzAizorFmxxFG21mVLfrjV++sXfUfxbblQ5E4OlgtX05lLBHcQxru7AA6myxdzbeJuef2rfHWQ8I+y2W+nVJpAkrNjmncZhU9C+NHdI76eJuMoKW2Aoik2AgADhjgWi99pXELfUysxYbQjIMcAspM4/52WpIV4KFZMJt9Xfnyv8oeo7qdkIw5YnbZaRlpxYic82ptnY1uSdyH8JcP30Om6/N1scC0E47hIW6bk5/jWda0fhsmzxgyFA/A55dLErU6H5IFzQOfkk= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="us-ascii" Content-ID: <5BDF97299AA57540AA815ECADEB34026@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: b157a93c-fc35-459b-96d2-08d64f075ac9 X-MS-Exchange-CrossTenant-originalarrivaltime: 20 Nov 2018 16:43:53.0092 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY2PR15MB0149 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-11-20_07:,, signatures=0 X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 20, 2018 at 08:36:04AM -0800, Tejun Heo wrote: > On Tue, Nov 20, 2018 at 04:33:11PM +0000, Roman Gushchin wrote: > > > If a non-frozen task is being moved into a frozen cgroup, shouldn't > > > that also trigger frozen state update? > >=20 > > It does! Just below these lines: > >=20 > > /* > > * If the task isn't in the desired state, force it to it. > > */ > > if (task->frozen !=3D test_bit(CGRP_FREEZE, &dst->flags)) > > cgroup_freeze_task(task, test_bit(CGRP_FREEZE, &dst->flags)); >=20 > But that wouldn't udpate the cgroup's frozen state and generate > notifications, right? Why? The task will be eventually trapped into cgroup_enter_frozen(), and from there cgroup_update_frozen() will be called. You are right, that notification will not be issued, because the cgroup is not changing its state (frozen->frozen). I'm not sure that it makes sense to change the cgroup state back and forth in this case. Are there any reasons I'm missing? Thanks!