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* FAILED: patch "[PATCH] sched/fair: Fix unthrottle_cfs_rq() for leaf_cfs_rq list" failed to apply to 5.4-stable tree
@ 2020-05-25 14:42 gregkh
  2020-05-25 17:27 ` Vincent Guittot
  0 siblings, 1 reply; 22+ messages in thread
From: gregkh @ 2020-05-25 14:42 UTC (permalink / raw)
  To: vincent.guittot, bsegall, pauld, peterz, zohooouoto; +Cc: stable


The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 39f23ce07b9355d05a64ae303ce20d1c4b92b957 Mon Sep 17 00:00:00 2001
From: Vincent Guittot <vincent.guittot@linaro.org>
Date: Wed, 13 May 2020 15:55:28 +0200
Subject: [PATCH] sched/fair: Fix unthrottle_cfs_rq() for leaf_cfs_rq list

Although not exactly identical, unthrottle_cfs_rq() and enqueue_task_fair()
are quite close and follow the same sequence for enqueuing an entity in the
cfs hierarchy. Modify unthrottle_cfs_rq() to use the same pattern as
enqueue_task_fair(). This fixes a problem already faced with the latter and
add an optimization in the last for_each_sched_entity loop.

Fixes: fe61468b2cb (sched/fair: Fix enqueue_task_fair warning)
Reported-by Tao Zhou <zohooouoto@zoho.com.cn>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Reviewed-by: Ben Segall <bsegall@google.com>
Link: https://lkml.kernel.org/r/20200513135528.4742-1-vincent.guittot@linaro.org

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c6d57c334d51..538ba5d94e99 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4774,7 +4774,6 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 	struct rq *rq = rq_of(cfs_rq);
 	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
 	struct sched_entity *se;
-	int enqueue = 1;
 	long task_delta, idle_task_delta;
 
 	se = cfs_rq->tg->se[cpu_of(rq)];
@@ -4798,26 +4797,44 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 	idle_task_delta = cfs_rq->idle_h_nr_running;
 	for_each_sched_entity(se) {
 		if (se->on_rq)
-			enqueue = 0;
+			break;
+		cfs_rq = cfs_rq_of(se);
+		enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
 
+		cfs_rq->h_nr_running += task_delta;
+		cfs_rq->idle_h_nr_running += idle_task_delta;
+
+		/* end evaluation on encountering a throttled cfs_rq */
+		if (cfs_rq_throttled(cfs_rq))
+			goto unthrottle_throttle;
+	}
+
+	for_each_sched_entity(se) {
 		cfs_rq = cfs_rq_of(se);
-		if (enqueue) {
-			enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
-		} else {
-			update_load_avg(cfs_rq, se, 0);
-			se_update_runnable(se);
-		}
+
+		update_load_avg(cfs_rq, se, UPDATE_TG);
+		se_update_runnable(se);
 
 		cfs_rq->h_nr_running += task_delta;
 		cfs_rq->idle_h_nr_running += idle_task_delta;
 
+
+		/* end evaluation on encountering a throttled cfs_rq */
 		if (cfs_rq_throttled(cfs_rq))
-			break;
+			goto unthrottle_throttle;
+
+		/*
+		 * One parent has been throttled and cfs_rq removed from the
+		 * list. Add it back to not break the leaf list.
+		 */
+		if (throttled_hierarchy(cfs_rq))
+			list_add_leaf_cfs_rq(cfs_rq);
 	}
 
-	if (!se)
-		add_nr_running(rq, task_delta);
+	/* At this point se is NULL and we are at root level*/
+	add_nr_running(rq, task_delta);
 
+unthrottle_throttle:
 	/*
 	 * The cfs_rq_throttled() breaks in the above iteration can result in
 	 * incomplete leaf list maintenance, resulting in triggering the
@@ -4826,7 +4843,8 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 	for_each_sched_entity(se) {
 		cfs_rq = cfs_rq_of(se);
 
-		list_add_leaf_cfs_rq(cfs_rq);
+		if (list_add_leaf_cfs_rq(cfs_rq))
+			break;
 	}
 
 	assert_list_leaf_cfs_rq(rq);


^ permalink raw reply related	[flat|nested] 22+ messages in thread
* Re: FAILED: patch "[PATCH] sched/fair: Fix unthrottle_cfs_rq() for leaf_cfs_rq list" failed to apply to 5.4-stable tree
@ 2020-11-19 14:56 Guilherme G. Piccoli
  2020-11-19 14:57 ` Guilherme Piccoli
                   ` (3 more replies)
  0 siblings, 4 replies; 22+ messages in thread
From: Guilherme G. Piccoli @ 2020-11-19 14:56 UTC (permalink / raw)
  To: Sasha Levin, peterz, Vincent Guittot
  Cc: bsegall, gregkh, pauld, zohooouoto, stable, Gavin Guo,
	nivedita.singhvi, halves, gpiccoli

Hi Sasha / Peter, is there anything blocking this backport from Vincent
to get merged in 5.4.y?

Thanks in advance,


Guilherme

^ permalink raw reply	[flat|nested] 22+ messages in thread

end of thread, other threads:[~2020-12-11  4:02 UTC | newest]

Thread overview: 22+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-05-25 14:42 FAILED: patch "[PATCH] sched/fair: Fix unthrottle_cfs_rq() for leaf_cfs_rq list" failed to apply to 5.4-stable tree gregkh
2020-05-25 17:27 ` Vincent Guittot
2020-05-26  0:22   ` Sasha Levin
2020-12-06  9:57   ` Greg KH
2020-12-06 11:25     ` Vincent Guittot
2020-12-06 11:40       ` Greg KH
2020-12-06 11:54         ` Vincent Guittot
2020-12-06 12:07           ` Greg KH
2020-12-06 12:10             ` Vincent Guittot
2020-12-06 15:18             ` Sasha Levin
2020-11-19 14:56 Guilherme G. Piccoli
2020-11-19 14:57 ` Guilherme Piccoli
     [not found]   ` <BN8PR12MB297872B12C4DBE0793605F9B9AE00@BN8PR12MB2978.namprd12.prod.outlook.com>
2020-11-19 17:45     ` Guilherme Piccoli
2020-11-19 18:57 ` Sasha Levin
2020-11-20  5:04   ` Nivedita Singhvi
2020-12-01 15:03 ` Guilherme G. Piccoli
2020-12-02  7:51   ` Greg KH
2020-12-02  8:21     ` Vincent Guittot
2020-12-02  9:44       ` Peter Zijlstra
2020-12-02 13:52         ` Sasha Levin
2020-12-06  9:57 ` Greg KH
2020-12-11  4:00   ` Nivedita Singhvi

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