Define atomic_exchange and atomic_decrement_if_positive if not already defined. ...

diff --git a/include/atomic.h b/include/atomic.h
index 813fb80..5177764 100644 (file)
--- a/include/atomic.h
+++ b/include/atomic.h
@@ -49,6 +49,24 @@
 #endif
 
 
+/* Store NEWVALUE in *MEM and return the old value.  */
+#ifndef atomic_exchange
+# define atomic_exchange(mem, newvalue) \
+  ({ __typeof (*mem) __oldval;                                               \
+     __typeof (mem) __memp = (mem);                                          \
+     __typeof (*mem) __value = (newvalue);                                   \
+                                                                             \
+     do                                                                              \
+       __oldval = (*__memp);                                                 \
+     while (__builtin_expect (atomic_compare_and_exchange_acq (__memp,       \
+                                                              __value,       \
+                                                              __oldval), 0));\
+                                                                             \
+     __oldval; })
+#endif
+
+
+/* Add VALUE to *MEM and return the old value of *MEM.  */
 #ifndef atomic_exchange_and_add
 # define atomic_exchange_and_add(mem, value) \
   ({ __typeof (*mem) __oldval;                                               \
@@ -57,10 +75,12 @@
                                                                              \
      do                                                                              \
        __oldval = (*__memp);                                                 \
-     while (atomic_compare_and_exchange_acq (__memp, __oldval + __value,      \
-                                            __oldval));                      \
+     while (__builtin_expect (atomic_compare_and_exchange_acq (__memp,       \
+                                                              __oldval       \
+                                                              + __value,     \
+                                                              __oldval), 0));\
                                                                              \
-     __oldval + __value; })
+     __oldval; })
 #endif
 
 
@@ -91,6 +111,26 @@
 #endif
 
 
+/* Decrement *MEM if it is > 0, and return the old value.  */
+#ifndef atomic_decrement_if_positive(mem) \
+  ({ __typeof (*mem) __val;                                                  \
+     __typeof (*mem) __oldval;                                               \
+     __typeof (mem) __memp;                                                  \
+                                                                             \
+     __val = *__memp;                                                        \
+     do                                                                              \
+       {                                                                     \
+        if (__builtin_expect (__val <= 0, 0))                                \
+          break;                                                             \
+        __oldval = __val;                                                    \
+        __val = atomic_compare_and_exchange_acq (__memp, __oldval - 1,       \
+                                                 __oldval);                  \
+       }                                                                     \
+     while (__builtin_expect (__val != __oldval, 0));                        \
+     __val; })
+#endif
+
+
 #ifndef atomic_add_negative
 # define atomic_add_negative(mem, value) \
   (atomic_exchange_and_add (mem, value) < 0)
@@ -117,8 +157,10 @@
                                                                              \
      do                                                                              \
        __oldval = (*__memp);                                                 \
-     while (atomic_compare_and_exchange_acq (__memp,                         \
-                                            __oldval | __mask, __oldval));   \
+     while (__builtin_expect (atomic_compare_and_exchange_acq (__memp,       \
+                                                              __oldval       \
+                                                              | __mask,      \
+                                                              __oldval), 0));\
                                                                              \
      __oldval & __mask; })
 #endif