1 files changed, 24 insertions, 0 deletions

diff --git a/include/linux/wait.h b/include/linux/wait.h
index ac38be2692d8..5bacfc4b336d 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -23,6 +23,7 @@ struct __wait_queue {
 struct wait_bit_key {
         void *flags;
         int bit_nr;
+#define WAIT_ATOMIC_T_BIT_NR -1
 };
 
 struct wait_bit_queue {
@@ -60,6 +61,9 @@ struct task_struct;
 #define __WAIT_BIT_KEY_INITIALIZER(word, bit)                           \
         { .flags = word, .bit_nr = bit, }
 
+#define __WAIT_ATOMIC_T_KEY_INITIALIZER(p)                              \
+        { .flags = p, .bit_nr = WAIT_ATOMIC_T_BIT_NR, }
+
 extern void __init_waitqueue_head(wait_queue_head_t *q, const char *name, struct lock_class_key *);
 
 #define init_waitqueue_head(q)                          \
@@ -146,8 +150,10 @@ void __wake_up_bit(wait_queue_head_t *, void *, int);
 int __wait_on_bit(wait_queue_head_t *, struct wait_bit_queue *, int (*)(void *), unsigned);
 int __wait_on_bit_lock(wait_queue_head_t *, struct wait_bit_queue *, int (*)(void *), unsigned);
 void wake_up_bit(void *, int);
+void wake_up_atomic_t(atomic_t *);
 int out_of_line_wait_on_bit(void *, int, int (*)(void *), unsigned);
 int out_of_line_wait_on_bit_lock(void *, int, int (*)(void *), unsigned);
+int out_of_line_wait_on_atomic_t(atomic_t *, int (*)(atomic_t *), unsigned);
 wait_queue_head_t *bit_waitqueue(void *, int);
 
 #define wake_up(x)                      __wake_up(x, TASK_NORMAL, 1, NULL)
@@ -896,5 +902,23 @@ static inline int wait_on_bit_lock(void *word, int bit,
                 return 0;
         return out_of_line_wait_on_bit_lock(word, bit, action, mode);
 }
+
+/**
+ * wait_on_atomic_t - Wait for an atomic_t to become 0
+ * @val: The atomic value being waited on, a kernel virtual address
+ * @action: the function used to sleep, which may take special actions
+ * @mode: the task state to sleep in
+ *
+ * Wait for an atomic_t to become 0.  We abuse the bit-wait waitqueue table for
+ * the purpose of getting a waitqueue, but we set the key to a bit number
+ * outside of the target 'word'.
+ */
+static inline
+int wait_on_atomic_t(atomic_t *val, int (*action)(atomic_t *), unsigned mode)
+{
+        if (atomic_read(val) == 0)
+                return 0;
+        return out_of_line_wait_on_atomic_t(val, action, mode);
+}
         
 #endif