Messages in this thread Patch in this message | | | Date | Tue, 21 Mar 2023 11:49:49 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2] sched/fair: sanitize vruntime of entity being migrated |
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On Tue, Mar 21, 2023 at 11:29:13AM +0100, Dietmar Eggemann wrote: > On 21/03/2023 11:02, Peter Zijlstra wrote: > > On Fri, Mar 17, 2023 at 05:08:10PM +0100, Vincent Guittot wrote: > >> Commit 829c1651e9c4 ("sched/fair: sanitize vruntime of entity being placed") > >> fixes an overflowing bug, but ignore a case that se->exec_start is reset > >> after a migration. > >> > >> For fixing this case, we delay the reset of se->exec_start after > >> placing the entity which se->exec_start to detect long sleeping task. > >> > >> In order to take into account a possible divergence between the clock_task > >> of 2 rqs, we increase the threshold to around 104 days. > >> > >> > >> Fixes: 829c1651e9c4 ("sched/fair: sanitize vruntime of entity being placed") > >> Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com> > >> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> > >> --- > > > > Blergh, this just isn't going to be nice. I'll go queue this for > > sched/urgent and then we can forget about this for a little while. > > > > Thanks! > > Don't we miss setting `se->exec_start = 0` for fair task in > move_queued_task()? ( ... and __migrate_swap_task()) > > https://lkml.kernel.org/r/df2cccda-1550-b06b-aa74-e0f054e9fb9d@arm.com
Ah, I see what you mean now... When I read your and Vincent's replies earlier today I though you mean to avoid the extra ENQUEUE_MIGRATED use, but your actual goal was to capure more sites.
Hmm, we could of course go add more ENQUEUE_MIGRATED, but you're right in that TASK_ON_RQ_MIGRATING already captures that.
An alternative is something like the below, that matches deactivate_task(), but still uses ENQUEUE_MIGRATED to pass it down into the class methods.
Hmm?
--- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2084,6 +2084,9 @@ static inline void dequeue_task(struct r void activate_task(struct rq *rq, struct task_struct *p, int flags) { + if (task_on_rq_migrating(p)) + flags |= ENQUEUE_MIGRATED; + enqueue_task(rq, p, flags); p->on_rq = TASK_ON_RQ_QUEUED; --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8726,7 +8726,7 @@ static void attach_task(struct rq *rq, s lockdep_assert_rq_held(rq); WARN_ON_ONCE(task_rq(p) != rq); - activate_task(rq, p, ENQUEUE_NOCLOCK | ENQUEUE_MIGRATED); + activate_task(rq, p, ENQUEUE_NOCLOCK); check_preempt_curr(rq, p, 0); }
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