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Subject[tip:sched/core] sched/balancing: Prevent the reselection of a previous env.dst_cpu if some tasks are pinned
Commit-ID:  7aff2e3a56b724b79fa2d5abd10d8231ef8fb0c5
Gitweb: http://git.kernel.org/tip/7aff2e3a56b724b79fa2d5abd10d8231ef8fb0c5
Author: Vladimir Davydov <vdavydov@parallels.com>
AuthorDate: Sun, 15 Sep 2013 21:30:13 +0400
Committer: Ingo Molnar <mingo@kernel.org>
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@parallels.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/281f59b6e596c718dd565ad267fc38f5b8e5c995.1379265590.git.vdavydov@parallels.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
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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