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Peter Anvin" , "Joel Fernandes, Google" , netdev , Jiri Olsa , Alasdair Kergon , Daniel Thompson , Davidlohr Bueso , Vincent Guittot , KVM list , Will Deacon , cgroups , x86 , Ingo Molnar , Mel Gorman , Jakub Kicinski , paulmck , linux-pm@vger.kernel.org, Boqun Feng , Jason Wessel , Josh Triplett , rostedt , linux-block@vger.kernel.org, linux-fsdevel , Borislav Petkov , Alexander Viro , Waiman Long , Namhyung Kim , Thomas Gleixner , acme , Dietmar Eggemann , Jens Axboe , Felipe Balbi , Stephen Boyd , Greg Kroah-Hartman , linux-usb@vger.kernel.org, "Rafael J. Wysocki" , Douglas Anderson , linux-kernel , linux-perf-users@vger.kernel.org, Johannes Weiner , Tejun Heo , John Stultz , Andrew Morton , rcu , bristot , "David S. Miller" Subject: Re: [dm-devel] [PATCH 3/6] sched, perf, kvm: Fix preemption condition X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dm-devel-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Wed, Jun 02, 2021 at 09:59:07AM -0400, Mathieu Desnoyers wrote: > ----- On Jun 2, 2021, at 9:12 AM, Peter Zijlstra peterz@infradead.org wrote: > > > When ran from the sched-out path (preempt_notifier or perf_event), > > p->state is irrelevant to determine preemption. You can get preempted > > with !task_is_running() just fine. > > > > The right indicator for preemption is if the task is still on the > > runqueue in the sched-out path. > > > > Signed-off-by: Peter Zijlstra (Intel) > > --- > > kernel/events/core.c | 7 +++---- > > virt/kvm/kvm_main.c | 2 +- > > 2 files changed, 4 insertions(+), 5 deletions(-) > > > > --- a/kernel/events/core.c > > +++ b/kernel/events/core.c > > @@ -8568,13 +8568,12 @@ static void perf_event_switch(struct tas > > }, > > }; > > > > - if (!sched_in && task->state == TASK_RUNNING) > > + if (!sched_in && current->on_rq) { > > This changes from checking task->state to current->on_rq, but this change > from "task" to "current" is not described in the commit message, which is odd. > > Are we really sure that task == current here ? Yeah, @task == @prev == current at this point, but yes, not sure why I changed that... lemme change that back to task. -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel