Commit 17f3f0be authored by Tianchen Ding's avatar Tianchen Ding Committed by Wen Zhiwei
Browse files

sched/fair: Make SCHED_IDLE entity be preempted in strict hierarchy 

stable inclusion
from stable-v6.6.54
commit 5a4f8de92dd7ddaa7ce33aa804cbad254b844b8f
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAZ3K2

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5a4f8de92dd7ddaa7ce33aa804cbad254b844b8f



--------------------------------

[ Upstream commit faa42d29419def58d3c3e5b14ad4037f0af3b496 ]

Consider the following cgroup:

                       root
                        |
             ------------------------
             |                      |
       normal_cgroup            idle_cgroup
             |                      |
   SCHED_IDLE task_A           SCHED_NORMAL task_B

According to the cgroup hierarchy, A should preempt B. But current
check_preempt_wakeup_fair() treats cgroup se and task separately, so B
will preempt A unexpectedly.
Unify the wakeup logic by {c,p}se_is_idle only. This makes SCHED_IDLE of
a task a relative policy that is effective only within its own cgroup,
similar to the behavior of NICE.

Also fix se_is_idle() definition when !CONFIG_FAIR_GROUP_SCHED.

Fixes: 30400039 ("sched: Cgroup SCHED_IDLE support")
Signed-off-by: default avatarTianchen Ding <dtcccc@linux.alibaba.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarJosh Don <joshdon@google.com>
Reviewed-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20240626023505.1332596-1-dtcccc@linux.alibaba.com


Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
Conflicts:
 kernel/sched/fair.c
Signed-off-by: default avatarWen Zhiwei <wenzhiwei@kylinos.cn>
parent 431dd11d

kernel/sched/fair.c

+9 −13
Original line number Diff line number Diff line
@@ -675,7 +675,7 @@ static int cfs_rq_is_idle(struct cfs_rq *cfs_rq) 


static int se_is_idle(struct sched_entity *se)

{

	return 0;

	return task_has_idle_policy(task_of(se));

}



#endif	/* CONFIG_FAIR_GROUP_SCHED */
@@ -9317,16 +9317,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ 
	if (test_tsk_need_resched(curr))

		return;



	/* Idle tasks are by definition preempted by non-idle tasks. */

	if (unlikely(task_has_idle_policy(curr)) &&

	    likely(!task_has_idle_policy(p)))

		goto preempt;



	/*

	 * Batch and idle tasks do not preempt non-idle tasks (their preemption

	 * is driven by the tick):

	 */

	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))

	if (!sched_feat(WAKEUP_PREEMPTION))

		return;



	find_matching_se(&se, &pse);
@@ -9336,7 +9327,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ 
	pse_is_idle = se_is_idle(pse);



	/*

	 * Preempt an idle group in favor of a non-idle group (and don't preempt

	 * Preempt an idle entity in favor of a non-idle entity (and don't preempt

	 * in the inverse case).

	 */

	if (cse_is_idle && !pse_is_idle)
@@ -9344,9 +9335,14 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ 
	if (cse_is_idle != pse_is_idle)

		return;



	/*

	 * BATCH and IDLE tasks do not preempt others.

	 */

	if (unlikely(p->policy != SCHED_NORMAL))

		return;



	cfs_rq = cfs_rq_of(se);

	update_curr(cfs_rq);



	/*

	 * XXX pick_eevdf(cfs_rq) != se ?

	 */