Messages in this thread | | | Date | Wed, 20 Jul 2022 14:50:15 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] nohz/full, sched/rt: Fix missed tick-reenabling bug in dequeue_task_rt |
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On Wed, Jul 13, 2022 at 07:18:42PM +0200, Nicolas Saenz Julienne wrote: > On Tue, 2022-06-28 at 11:22 +0200, Nicolas Saenz Julienne wrote: > > dequeue_task_rt() only decrements 'rt_rq->rt_nr_running' after having > > called sched_update_tick_dependency() preventing it from re-enabling the > > tick on systems that no longer have pending SCHED_RT tasks but have > > multiple runnable SCHED_OTHER tasks: > > > > dequeue_task_rt() > > dequeue_rt_entity() > > dequeue_rt_stack() > > dequeue_top_rt_rq() > > sub_nr_running() // decrements rq->nr_running > > sched_update_tick_dependency() > > sched_can_stop_tick() // checks rq->rt.rt_nr_running, > > ... > > __dequeue_rt_entity() > > dec_rt_tasks() // decrements rq->rt.rt_nr_running > > ... > > > > Every other scheduler class performs the operation in the opposite > > order, and sched_update_tick_dependency() expects the values to be > > updated as such. So avoid the misbehaviour by inverting the order in > > which the above operations are performed in the RT scheduler. > > > > Fixes: 76d92ac305f2 ("sched: Migrate sched to use new tick dependency mask model") > > Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com> > > --- > > Ping :)
Thanks! got stuck in the retbleed backlog :/
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