From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleg Nesterov Subject: Re: [PATCH v2 3/6] cgroup: cgroup v2 freezer Date: Tue, 13 Nov 2018 17:00:04 +0100 Message-ID: <20181113160003.GD30990@redhat.com> References: <20181112230422.5911-1-guro@fb.com> <20181112230422.5911-5-guro@fb.com> <20181113153700.GB30990@redhat.com> <20181113154349.GF2509588@devbig004.ftw2.facebook.com> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20181113154349.GF2509588@devbig004.ftw2.facebook.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Tejun Heo Cc: Roman Gushchin , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Roman Gushchin Hi Tejun, On 11/13, Tejun Heo wrote: > > > OK, please forget for now, but perhaps it would be more clean to add > > JOBCTL_TRAP_FREEZE to the JOBCTL_PENDING_MASK check in recalc_sigpending() > > and change get_signal to check JOBCTL_TRAP_MASK | JOBCTL_TRAP_FREEZE; and > > I am not even sure cgroup_freezer_enter() should live in do_jobctl_trap(). > > I'm sure you're aware of the context but just to refresh - one thing > which was really broken about cgroup1 freezer was that it piggybacked > on hibernation freezer and put frozen tasks in a state which is > undefined when seen from userspace - they're just stuck in D sleep > somewhere in the kernel. That's fine when the whole system is not > gonna be running, but not when only a subportion is being frozen. Thanks, I see. > So, the primary goal of cgroup2 freezer is putting the tasks in an > equivalent state as jobctl stop. It's a jobctl stop but controlled by > cgroup frozen state, meaning that they can be killed, PTRACE_SEIZE'd > and INTERRUPT'ed (PTRACE_ATTACH doesn't work as signal delivery should > be blocked but that's fine) and so on. And I agree, JOBCTL_TRAP_FREEZE looks fine. Just somehow I _feel_ that we can improve this logic a bit, but let me repeat that of course I can be easily wrong and I didn't even read the patch yet. Oleg.