From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleg Nesterov Subject: Re: [PATCH v10 4/9] cgroup: cgroup v2 freezer Date: Fri, 26 Apr 2019 19:40:19 +0200 Message-ID: <20190426174019.GB24755@redhat.com> References: <20190405174708.1010-1-guro@fb.com> <20190405174708.1010-5-guro@fb.com> <20190419151912.GA12152@redhat.com> <20190419161118.GA23357@tower.DHCP.thefacebook.com> <20190419162600.GC12228@redhat.com> <20190419165600.GC23357@tower.DHCP.thefacebook.com> <20190420105838.GA17468@redhat.com> <20190422221116.GA10341@tower.DHCP.thefacebook.com> <20190424154619.GG16167@redhat.com> <20190424220634.GA22896@tower.DHCP.thefacebook.com> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20190424220634.GA22896@tower.DHCP.thefacebook.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Roman Gushchin Cc: Roman Gushchin , Tejun Heo , Kernel Team , "cgroups@vger.kernel.org" , "linux-kernel@vger.kernel.org" On 04/24, Roman Gushchin wrote: > > On Wed, Apr 24, 2019 at 05:46:19PM +0200, Oleg Nesterov wrote: > > > > OK, how about the ABSOLUTELY UNTESTED patch below? For the start. > > It looks good to me (and all freezer selftests pass). > > Just to be sure, is it a solution to avoid the busy loop in the signal handling > loop, right? Yes, > Because it doesn't allow to drop the ->frozen check from recalc(). Yes. Because we can race with unfreeze after leave_frozen(). > The JOBCTL_TRAP_FREEZE check without siglock initially looked dangerous to me, > but after some thoughts I didn't find any case when it's wrong. I think this is fine... Yes, JOBCTL_TRAP_FREEZE can be already set when we take siglock, but I don't think we need to recheck this flag. The only important thing (afaics) is that CGRP_FREEZE is stable under css_set_lock, so we can't wrongly set TRAP_FREEZE. > Do you prefer me to master a patch Yes please ;) Oleg.