[tip:sched/core] sched/balancing: Prevent the reselection of a previous env.dst_cpu if some tasks are pinned

[tip-bot for Vladimir Davydov]

Commit-ID:  7aff2e3a56b724b79fa2d5abd10d8231ef8fb0c5
Gitweb:     http://git.kernel.org/tip/7aff2e3a56b724b79fa2d5abd10d8231ef8fb0c5
Author:     Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
AuthorDate: Sun, 15 Sep 2013 21:30:13 +0400
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 20 Sep 2013 12:02:20 +0200

sched/balancing: Prevent the reselection of a previous env.dst_cpu if some tasks are pinned

Currently new_dst_cpu is prevented from being reselected actually, not
dst_cpu. This can result in attempting to pull tasks to this_cpu twice.

Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/281f59b6e596c718dd565ad267fc38f5b8e5c995.1379265590.git.vdavydov@xxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/sched/fair.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 71c6ef5..0784ab6 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5261,15 +5261,15 @@ more_balance:
 		 */
 		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
 
+			/* Prevent to re-select dst_cpu via env's cpus */
+			cpumask_clear_cpu(env.dst_cpu, env.cpus);
+
 			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
 			env.dst_cpu	 = env.new_dst_cpu;
 			env.flags	&= ~LBF_DST_PINNED;
 			env.loop	 = 0;
 			env.loop_break	 = sched_nr_migrate_break;
 
-			/* Prevent to re-select dst_cpu via env's cpus */
-			cpumask_clear_cpu(env.dst_cpu, env.cpus);
-
 			/*
 			 * Go back to "more_balance" rather than "redo" since we
 			 * need to continue with same src_cpu.
--
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