sched: Simplify mutex_spin_on_owner()

[firefly-linux-kernel-4.4.55.git] / kernel / sched.c

diff --git a/kernel/sched.c b/kernel/sched.c
index 59252754fbe0a84e35de2d2e8f943cdb50a1cb84..e355ee72e83fbc1e611448ca2705c5fe426c1dec 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4306,11 +4306,8 @@ EXPORT_SYMBOL(schedule);
 
 static inline bool owner_running(struct mutex *lock, struct task_struct *owner)
 {
-       bool ret = false;
-
-       rcu_read_lock();
        if (lock->owner != owner)
-               goto fail;
+               return false;
 
        /*
         * Ensure we emit the owner->on_cpu, dereference _after_ checking
@@ -4320,11 +4317,7 @@ static inline bool owner_running(struct mutex *lock, struct task_struct *owner)
         */
        barrier();
 
-       ret = owner->on_cpu;
-fail:
-       rcu_read_unlock();
-
-       return ret;
+       return owner->on_cpu;
 }
 
 /*
@@ -4336,21 +4329,21 @@ int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
        if (!sched_feat(OWNER_SPIN))
                return 0;
 
+       rcu_read_lock();
        while (owner_running(lock, owner)) {
                if (need_resched())
-                       return 0;
+                       break;
 
                arch_mutex_cpu_relax();
        }
+       rcu_read_unlock();
 
        /*
-        * If the owner changed to another task there is likely
-        * heavy contention, stop spinning.
+        * We break out the loop above on need_resched() and when the
+        * owner changed, which is a sign for heavy contention. Return
+        * success only when lock->owner is NULL.
         */
-       if (lock->owner)
-               return 0;
-
-       return 1;
+       return lock->owner == NULL;
 }
 #endif