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Subject[tip:sched/urgent] sched/deadline: Fix double accounting of rq/running bw in push & pull
Commit-ID:  f4904815f97a934258445a8f763f6b6c48f007e7
Gitweb: https://git.kernel.org/tip/f4904815f97a934258445a8f763f6b6c48f007e7
Author: Dietmar Eggemann <dietmar.eggemann@arm.com>
AuthorDate: Fri, 2 Aug 2019 15:59:43 +0100
Committer: Peter Zijlstra <peterz@infradead.org>
CommitDate: Tue, 6 Aug 2019 12:49:18 +0200

sched/deadline: Fix double accounting of rq/running bw in push & pull

{push,pull}_dl_task() always calls {de,}activate_task() with .flags=0
which sets p->on_rq=TASK_ON_RQ_MIGRATING.

{push,pull}_dl_task()->{de,}activate_task()->{de,en}queue_task()->
{de,en}queue_task_dl() calls {sub,add}_{running,rq}_bw() since
p->on_rq==TASK_ON_RQ_MIGRATING.
So {sub,add}_{running,rq}_bw() in {push,pull}_dl_task() is
double-accounting for that task.

Fix it by removing rq/running bw accounting in [push/pull]_dl_task().

Fixes: 7dd778841164 ("sched/core: Unify p->on_rq updates")
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Luca Abeni <luca.abeni@santannapisa.it>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Qais Yousef <qais.yousef@arm.com>
Link: https://lkml.kernel.org/r/20190802145945.18702-2-dietmar.eggemann@arm.com
---
kernel/sched/deadline.c | 8 --------
1 file changed, 8 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index ef5b9f6b1d42..46122edd8552 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2088,17 +2088,13 @@ retry:
}

deactivate_task(rq, next_task, 0);
- sub_running_bw(&next_task->dl, &rq->dl);
- sub_rq_bw(&next_task->dl, &rq->dl);
set_task_cpu(next_task, later_rq->cpu);
- add_rq_bw(&next_task->dl, &later_rq->dl);

/*
* Update the later_rq clock here, because the clock is used
* by the cpufreq_update_util() inside __add_running_bw().
*/
update_rq_clock(later_rq);
- add_running_bw(&next_task->dl, &later_rq->dl);
activate_task(later_rq, next_task, ENQUEUE_NOCLOCK);
ret = 1;

@@ -2186,11 +2182,7 @@ static void pull_dl_task(struct rq *this_rq)
resched = true;

deactivate_task(src_rq, p, 0);
- sub_running_bw(&p->dl, &src_rq->dl);
- sub_rq_bw(&p->dl, &src_rq->dl);
set_task_cpu(p, this_cpu);
- add_rq_bw(&p->dl, &this_rq->dl);
- add_running_bw(&p->dl, &this_rq->dl);
activate_task(this_rq, p, 0);
dmin = p->dl.deadline;

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