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Revert "sched/fair: Remove dead code on enqueue_task_fair()"

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This reverts commit 819224e506.

The cfs_rq->curr == se case can actually happen with CFS_BANDWIDTH,
so the removed code is needed. Document this.

Fixes: 819224e506 ("sched/fair: Remove dead code on enqueue_task_fair()")
Reported-by: Christian Loehle <christian.loehle@arm.com>
Signed-off-by: Kayra Cizmeci <kayracizmeci@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/lkml/fd3f9d83-cb5b-496b-b7c1-b40f31cf795e@arm.com/
Link: https://patch.msgid.link/20261015082919.4344-1-kayracizmeci@gmail.com
This commit is contained in:
Kayra Cizmeci 2026-10-15 11:29:18 +03:00 committed by Peter Zijlstra
parent fcceb7da94
commit 0a94d0ea8d
1 changed files with 15 additions and 3 deletions
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18
kernel/sched/fair.c
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@ -8156,6 +8156,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
struct sched_entity *se = &p->se;
struct cfs_rq *cfs_rq = &rq->cfs;
unsigned long weight;
bool curr;
if (task_is_throttled(p) && enqueue_throttled_task(p))
return;
@ -8184,14 +8185,25 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
if (p->in_iowait)
cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
curr = (cfs_rq->curr == se);
/*
* This can actually happen with CFS_BANDWIDTH, a task can be throttled
* and dequeued, unthrottled from another CPU and then enqueued again
* before schedule().
*/
if (curr)
place_entity(cfs_rq, se, flags);
if (se->on_rq && se->sched_delayed)
requeue_delayed_entity(cfs_rq, se);
weight = enqueue_hierarchy(p, flags);
reweight_eevdf(cfs_rq, se, weight, false);
place_entity(cfs_rq, se, flags | ENQUEUE_QUEUED);
__enqueue_entity(cfs_rq, se);
if (!curr) {
reweight_eevdf(cfs_rq, se, weight, false);
place_entity(cfs_rq, se, flags | ENQUEUE_QUEUED);
__enqueue_entity(cfs_rq, se);
}
if (!rq_h_nr_queued && rq->cfs.h_nr_queued)
dl_server_start(&rq->fair_server);