2 files changed, 28 insertions, 0 deletions

diff --git a/include/linux/semaphore.h b/include/linux/semaphore.h
index b3c691b089b2..88f2a28cc0f1 100644
--- a/include/linux/semaphore.h
+++ b/include/linux/semaphore.h
@@ -62,6 +62,12 @@ extern void down(struct semaphore *sem);
 extern int __must_check down_interruptible(struct semaphore *sem);
 
 /*
+ * As down_interruptible(), except the sleep may only be interrupted by
+ * signals which are fatal to this process.
+ */
+extern int __must_check down_killable(struct semaphore *sem);
+
+/*
  * As down(), except this function will not sleep.  It will return 0 if it
  * acquired the semaphore and 1 if the semaphore was contended.  This
  * function may be called from any context, including interrupt and softirq.
diff --git a/kernel/semaphore.c b/kernel/semaphore.c
index d5a72702f261..2da2aed950f3 100644
--- a/kernel/semaphore.c
+++ b/kernel/semaphore.c
@@ -34,6 +34,7 @@
 
 static noinline void __down(struct semaphore *sem);
 static noinline int __down_interruptible(struct semaphore *sem);
+static noinline int __down_killable(struct semaphore *sem);
 static noinline void __up(struct semaphore *sem);
 
 void down(struct semaphore *sem)
@@ -61,6 +62,20 @@ int down_interruptible(struct semaphore *sem)
 }
 EXPORT_SYMBOL(down_interruptible);
 
+int down_killable(struct semaphore *sem)
+{
+        unsigned long flags;
+        int result = 0;
+
+        spin_lock_irqsave(&sem->lock, flags);
+        if (unlikely(sem->count-- <= 0))
+                result = __down_killable(sem);
+        spin_unlock_irqrestore(&sem->lock, flags);
+
+        return result;
+}
+EXPORT_SYMBOL(down_killable);
+
 /**
  * down_trylock - try to acquire the semaphore, without waiting
  * @sem: the semaphore to be acquired
@@ -143,6 +158,8 @@ static inline int __sched __down_common(struct semaphore *sem, long state)
         for (;;) {
                 if (state == TASK_INTERRUPTIBLE && signal_pending(task))
                         goto interrupted;
+                if (state == TASK_KILLABLE && fatal_signal_pending(task))
+                        goto interrupted;
                 __set_task_state(task, state);
                 spin_unlock_irq(&sem->lock);
                 schedule();
@@ -178,6 +195,11 @@ static noinline int __sched __down_interruptible(struct semaphore *sem)
         return __down_common(sem, TASK_INTERRUPTIBLE);
 }
 
+static noinline int __sched __down_killable(struct semaphore *sem)
+{
+        return __down_common(sem, TASK_KILLABLE);
+}
+
 static noinline void __sched __up(struct semaphore *sem)
 {
         if (unlikely(list_empty(&sem->wait_list)))