1 files changed, 8 insertions, 17 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index f475c608b073..165b532dd8c2 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2280,6 +2280,9 @@ void task_oncpu_function_call(struct task_struct *p,
 }
 
 #ifdef CONFIG_SMP
+/*
+ * ->cpus_allowed is protected by either TASK_WAKING or rq->lock held.
+ */
 static int select_fallback_rq(int cpu, struct task_struct *p)
 {
         int dest_cpu;
@@ -2316,12 +2319,7 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
 }
 
 /*
- * Gets called from 3 sites (exec, fork, wakeup), since it is called without
- * holding rq->lock we need to ensure ->cpus_allowed is stable, this is done
- * by:
- *
- *  exec:           is unstable, retry loop
- *  fork & wake-up: serialize ->cpus_allowed against TASK_WAKING
+ * The caller (fork, wakeup) owns TASK_WAKING, ->cpus_allowed is stable.
  */
 static inline
 int select_task_rq(struct task_struct *p, int sd_flags, int wake_flags)
@@ -3076,9 +3074,8 @@ void sched_exec(void)
         unsigned long flags;
         struct rq *rq;
 
-again:
         this_cpu = get_cpu();
-        dest_cpu = select_task_rq(p, SD_BALANCE_EXEC, 0);
+        dest_cpu = p->sched_class->select_task_rq(p, SD_BALANCE_EXEC, 0);
         if (dest_cpu == this_cpu) {
                 put_cpu();
                 return;
@@ -3086,18 +3083,12 @@ again:
 
         rq = task_rq_lock(p, &flags);
         put_cpu();
-
         /*
          * select_task_rq() can race against ->cpus_allowed
          */
-        if (!cpumask_test_cpu(dest_cpu, &p->cpus_allowed)
-            || unlikely(!cpu_active(dest_cpu))) {
-                task_rq_unlock(rq, &flags);
-                goto again;
-        }
-
-        /* force the process onto the specified CPU */
-        if (migrate_task(p, dest_cpu, &req)) {
+        if (cpumask_test_cpu(dest_cpu, &p->cpus_allowed) &&
+            likely(cpu_active(dest_cpu)) &&
+            migrate_task(p, dest_cpu, &req)) {
                 /* Need to wait for migration thread (might exit: take ref). */
                 struct task_struct *mt = rq->migration_thread;