sched: Reset loop counters if all tasks are pinned and we need to redo load balance

While load balancing, if all tasks on the source runqueue are pinned,
we retry after excluding the corresponding source cpu. However, loop counters
env.loop and env.loop_break are not reset before retrying, which can lead
to failure in moving the tasks. In this patch we reset env.loop and
env.loop_break to their inital values before we retry.

Signed-off-by: Prashanth Nageshappa <prashanth@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4FE06EEF.2090709@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9361669d42422da202f5d6402a1d195e5a051b28..f9f9aa0edf3c47f8731d4a7f43ca3ef1872fdfce 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4288,8 +4288,11 @@ more_balance:
                /* All tasks on this runqueue were pinned by CPU affinity */
                if (unlikely(env.flags & LBF_ALL_PINNED)) {
                        cpumask_clear_cpu(cpu_of(busiest), cpus);
-                       if (!cpumask_empty(cpus))
+                       if (!cpumask_empty(cpus)) {
+                               env.loop = 0;
+                               env.loop_break = sched_nr_migrate_break;
                                goto redo;
+                       }
                        goto out_balanced;
                }
        }