From: Uladzislau Rezki <urezki@gmail.com>
To: Ingo Molnar <mingo@redhat.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Uladzislau 2 Rezki <uladzislau2.rezki@sonymobile.com>
Subject: [RFC,v2 1/3] sched: set loop_max after rq lock is taken
Date: Wed, 8 Feb 2017 09:43:27 +0100 [thread overview]
Message-ID: <1486543409-11493-1-git-send-email-urezki@gmail.com> (raw)
From: Uladzislau 2 Rezki <uladzislau2.rezki@sonymobile.com>
While doing a load balance there is a race in setting
loop_max variable since nr_running can be changed causing
incorect iteration loops.
As a result we may skip some candidates or check the same
tasks again.
Signed-off-by: Uladzislau 2 Rezki <uladzislau2.rezki@sonymobile.com>
---
kernel/sched/fair.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6559d19..4be7193 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8073,12 +8073,17 @@ static int load_balance(int this_cpu, struct rq *this_rq,
* correctly treated as an imbalance.
*/
env.flags |= LBF_ALL_PINNED;
- env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
more_balance:
raw_spin_lock_irqsave(&busiest->lock, flags);
/*
+ * Set loop_max when rq's lock is taken to prevent a race.
+ */
+ env.loop_max = min(sysctl_sched_nr_migrate,
+ busiest->nr_running);
+
+ /*
* cur_ld_moved - load moved in current iteration
* ld_moved - cumulative load moved across iterations
*/
--
2.1.4
next reply other threads:[~2017-02-08 8:52 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-08 8:43 Uladzislau Rezki [this message]
2017-02-08 8:43 ` [RFC,v2 2/3] sched: set number of iterations to h_nr_running Uladzislau Rezki
2017-02-09 12:20 ` Peter Zijlstra
2017-02-09 18:59 ` Uladzislau Rezki
2017-02-08 8:43 ` [RFC,v2 3/3] sched: ignore task_h_load for CPU_NEWLY_IDLE Uladzislau Rezki
2017-02-08 9:19 ` Mike Galbraith
2017-02-09 10:12 ` Uladzislau Rezki
2017-02-09 12:22 ` Peter Zijlstra
2017-02-09 18:54 ` Uladzislau Rezki
2017-02-13 13:51 ` Peter Zijlstra
2017-02-13 17:17 ` Uladzislau Rezki
2017-02-14 18:28 ` Uladzislau Rezki
2017-02-15 18:58 ` Dietmar Eggemann
2017-02-16 11:20 ` Uladzislau Rezki
2017-03-08 15:35 ` Uladzislau Rezki
2017-02-09 12:14 ` [RFC,v2 1/3] sched: set loop_max after rq lock is taken Peter Zijlstra
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