1 files changed, 34 insertions, 30 deletions

diff --git a/kernel/semaphore.c b/kernel/semaphore.c
index 5e41217239e8..5c2942e768cd 100644
--- a/kernel/semaphore.c
+++ b/kernel/semaphore.c
@@ -54,9 +54,10 @@ void down(struct semaphore *sem)
         unsigned long flags;
 
         spin_lock_irqsave(&sem->lock, flags);
-        if (unlikely(!sem->count))
+        if (likely(sem->count > 0))
+                sem->count--;
+        else
                 __down(sem);
-        sem->count--;
         spin_unlock_irqrestore(&sem->lock, flags);
 }
 EXPORT_SYMBOL(down);
@@ -76,10 +77,10 @@ int down_interruptible(struct semaphore *sem)
         int result = 0;
 
         spin_lock_irqsave(&sem->lock, flags);
-        if (unlikely(!sem->count))
-                result = __down_interruptible(sem);
-        if (!result)
+        if (likely(sem->count > 0))
                 sem->count--;
+        else
+                result = __down_interruptible(sem);
         spin_unlock_irqrestore(&sem->lock, flags);
 
         return result;
@@ -102,10 +103,10 @@ int down_killable(struct semaphore *sem)
         int result = 0;
 
         spin_lock_irqsave(&sem->lock, flags);
-        if (unlikely(!sem->count))
-                result = __down_killable(sem);
-        if (!result)
+        if (likely(sem->count > 0))
                 sem->count--;
+        else
+                result = __down_killable(sem);
         spin_unlock_irqrestore(&sem->lock, flags);
 
         return result;
@@ -156,10 +157,10 @@ int down_timeout(struct semaphore *sem, long jiffies)
         int result = 0;
 
         spin_lock_irqsave(&sem->lock, flags);
-        if (unlikely(!sem->count))
-                result = __down_timeout(sem, jiffies);
-        if (!result)
+        if (likely(sem->count > 0))
                 sem->count--;
+        else
+                result = __down_timeout(sem, jiffies);
         spin_unlock_irqrestore(&sem->lock, flags);
 
         return result;
@@ -178,8 +179,9 @@ void up(struct semaphore *sem)
         unsigned long flags;
 
         spin_lock_irqsave(&sem->lock, flags);
-        sem->count++;
-        if (unlikely(!list_empty(&sem->wait_list)))
+        if (likely(list_empty(&sem->wait_list)))
+                sem->count++;
+        else
                 __up(sem);
         spin_unlock_irqrestore(&sem->lock, flags);
 }
@@ -190,6 +192,7 @@ EXPORT_SYMBOL(up);
 struct semaphore_waiter {
         struct list_head list;
         struct task_struct *task;
+        int up;
 };
 
 /*
@@ -202,34 +205,33 @@ static inline int __sched __down_common(struct semaphore *sem, long state,
 {
         struct task_struct *task = current;
         struct semaphore_waiter waiter;
-        int ret = 0;
 
-        waiter.task = task;
         list_add_tail(&waiter.list, &sem->wait_list);
+        waiter.task = task;
+        waiter.up = 0;
 
         for (;;) {
-                if (state == TASK_INTERRUPTIBLE && signal_pending(task)) {
-                        ret = -EINTR;
-                        break;
-                }
-                if (state == TASK_KILLABLE && fatal_signal_pending(task)) {
-                        ret = -EINTR;
-                        break;
-                }
-                if (timeout <= 0) {
-                        ret = -ETIME;
-                        break;
-                }
+                if (state == TASK_INTERRUPTIBLE && signal_pending(task))
+                        goto interrupted;
+                if (state == TASK_KILLABLE && fatal_signal_pending(task))
+                        goto interrupted;
+                if (timeout <= 0)
+                        goto timed_out;
                 __set_task_state(task, state);
                 spin_unlock_irq(&sem->lock);
                 timeout = schedule_timeout(timeout);
                 spin_lock_irq(&sem->lock);
-                if (sem->count > 0)
-                        break;
+                if (waiter.up)
+                        return 0;
         }
 
+ timed_out:
+        list_del(&waiter.list);
+        return -ETIME;
+
+ interrupted:
         list_del(&waiter.list);
-        return ret;
+        return -EINTR;
 }
 
 static noinline void __sched __down(struct semaphore *sem)
@@ -256,5 +258,7 @@ static noinline void __sched __up(struct semaphore *sem)
 {
         struct semaphore_waiter *waiter = list_first_entry(&sem->wait_list,
                                                 struct semaphore_waiter, list);
+        list_del(&waiter->list);
+        waiter->up = 1;
         wake_up_process(waiter->task);
 }