sched: move_task_off_dead_cpu(): Remove retry logic

The previous patch preserved the retry logic, but it looks unneeded.

__migrate_task() can only fail if we raced with migration after we dropped
the lock, but in this case the caller of set_cpus_allowed/etc must initiate
migration itself if ->on_rq == T.

We already fixed p->cpus_allowed, the changes in active/online masks must
be visible to racer, it should migrate the task to online cpu correctly.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100315091014.GA9138@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 6 insertions, 7 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 27774b5aeb61..f475c608b073 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5456,7 +5456,7 @@ static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
         struct rq *rq = cpu_rq(dead_cpu);
         int needs_cpu, uninitialized_var(dest_cpu);
         unsigned long flags;
-again:
+
         local_irq_save(flags);
 
         raw_spin_lock(&rq->lock);
@@ -5464,14 +5464,13 @@ again:
         if (needs_cpu)
                 dest_cpu = select_fallback_rq(dead_cpu, p);
         raw_spin_unlock(&rq->lock);
-
-        /* It can have affinity changed while we were choosing. */
+        /*
+         * It can only fail if we race with set_cpus_allowed(),
+         * in the racer should migrate the task anyway.
+         */
         if (needs_cpu)
-                needs_cpu = !__migrate_task(p, dead_cpu, dest_cpu);
+                __migrate_task(p, dead_cpu, dest_cpu);
         local_irq_restore(flags);
-
-        if (unlikely(needs_cpu))
-                goto again;
 }
 
 /*