From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juri Lelli Subject: Re: [PATCH v8 6/8] cgroup/cpuset: Change cpuset_rwsem and hotplug lock order Date: Mon, 1 Jul 2019 08:52:33 +0200 Message-ID: <20190701065233.GA26005@localhost.localdomain> References: <20190628080618.522-1-juri.lelli@redhat.com> <20190628080618.522-7-juri.lelli@redhat.com> <20190628130308.GU3419@hirez.programming.kicks-ass.net> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20190628130308.GU3419@hirez.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Peter Zijlstra Cc: mingo@redhat.com, rostedt@goodmis.org, tj@kernel.org, linux-kernel@vger.kernel.org, luca.abeni@santannapisa.it, claudio@evidence.eu.com, tommaso.cucinotta@santannapisa.it, bristot@redhat.com, mathieu.poirier@linaro.org, lizefan@huawei.com, cgroups@vger.kernel.org, Prateek Sood Hi, On 28/06/19 15:03, Peter Zijlstra wrote: > On Fri, Jun 28, 2019 at 10:06:16AM +0200, Juri Lelli wrote: > > cpuset_rwsem is going to be acquired from sched_setscheduler() with a > > following patch. There are however paths (e.g., spawn_ksoftirqd) in > > which sched_scheduler() is eventually called while holding hotplug lock; > > this creates a dependecy between hotplug lock (to be always acquired > > first) and cpuset_rwsem (to be always acquired after hotplug lock). > > > > Fix paths which currently take the two locks in the wrong order (after > > a following patch is applied). > > Signed-off-by: Juri Lelli > > This all reminds me of this: > > https://lkml.kernel.org/r/1510755615-25906-1-git-send-email-prsood@codeaurora.org > > Which sadly got reverted again. If we do this now (I've always been a > proponent), then we can make that rebuild synchronous again, which > should also help here IIRC. Why was that reverted? Perf regression of some type? Thanks, Juri