Atomic/SMP update, part 2.

Added new atomic functions, renamed some old ones.  Some #defines have
been added for backward compatibility.

Merged the pre- and post-ARMv6 implementations into a single file.

Renamed the semi-private __android_membar_full_smp to USE_SCREAMING_CAPS
since that's more appropriate for a macro.

Added lots of comments.

Note Mac OS X primitives have not been tested.

Change-Id: If827260750aeb61ad5c2b760e30658e29dbb26f2

1 files changed, 38 insertions, 14 deletions

diff --git a/libcutils/atomic-android-sh.c b/libcutils/atomic-android-sh.c
index d95b02b..abe7d25 100644
--- a/libcutils/atomic-android-sh.c
+++ b/libcutils/atomic-android-sh.c
@@ -35,6 +35,9 @@
  *     ARM implementation, in this file above.
  *     We follow the fact that the initializer for mutex is a simple zero
  *     value.
+ *
+ * (3) These operations are NOT safe for SMP, as there is no currently
+ *     no definition for a memory barrier operation.
  */
 
 #include <pthread.h>
@@ -46,18 +49,35 @@ static pthread_mutex_t  _swap_locks[SWAP_LOCK_COUNT];
    &_swap_locks[((unsigned)(void*)(addr) >> 3U) % SWAP_LOCK_COUNT]
 
 
-void android_atomic_write(int32_t value, volatile int32_t* addr) {
+int32_t android_atomic_acquire_load(volatile int32_t* addr)
+{
+    return *addr;
+}
+
+int32_t android_atomic_release_load(volatile int32_t* addr)
+{
+    return *addr;
+}
+
+void android_atomic_acquire_store(int32_t value, volatile int32_t* addr) {
     int32_t oldValue;
     do {
         oldValue = *addr;
-    } while (android_atomic_cmpxchg(oldValue, value, addr));
+    } while (android_atomic_release_cas(oldValue, value, addr));
+}
+
+void android_atomic_release_store(int32_t value, volatile int32_t* addr) {
+    int32_t oldValue;
+    do {
+        oldValue = *addr;
+    } while (android_atomic_release_cas(oldValue, value, addr));
 }
 
 int32_t android_atomic_inc(volatile int32_t* addr) {
     int32_t oldValue;
     do {
         oldValue = *addr;
-    } while (android_atomic_cmpxchg(oldValue, oldValue+1, addr));
+    } while (android_atomic_release_cas(oldValue, oldValue+1, addr));
     return oldValue;
 }
 
@@ -65,7 +85,7 @@ int32_t android_atomic_dec(volatile int32_t* addr) {
     int32_t oldValue;
     do {
         oldValue = *addr;
-    } while (android_atomic_cmpxchg(oldValue, oldValue-1, addr));
+    } while (android_atomic_release_cas(oldValue, oldValue-1, addr));
     return oldValue;
 }
 
@@ -73,7 +93,7 @@ int32_t android_atomic_add(int32_t value, volatile int32_t* addr) {
     int32_t oldValue;
     do {
         oldValue = *addr;
-    } while (android_atomic_cmpxchg(oldValue, oldValue+value, addr));
+    } while (android_atomic_release_cas(oldValue, oldValue+value, addr));
     return oldValue;
 }
 
@@ -81,7 +101,7 @@ int32_t android_atomic_and(int32_t value, volatile int32_t* addr) {
     int32_t oldValue;
     do {
         oldValue = *addr;
-    } while (android_atomic_cmpxchg(oldValue, oldValue&value, addr));
+    } while (android_atomic_release_cas(oldValue, oldValue&value, addr));
     return oldValue;
 }
 
@@ -89,11 +109,15 @@ int32_t android_atomic_or(int32_t value, volatile int32_t* addr) {
     int32_t oldValue;
     do {
         oldValue = *addr;
-    } while (android_atomic_cmpxchg(oldValue, oldValue|value, addr));
+    } while (android_atomic_release_cas(oldValue, oldValue|value, addr));
     return oldValue;
 }
 
-int32_t android_atomic_swap(int32_t value, volatile int32_t* addr) {
+int32_t android_atomic_acquire_swap(int32_t value, volatile int32_t* addr) {
+    return android_atomic_release_swap(value, addr);
+}
+
+int32_t android_atomic_release_swap(int32_t value, volatile int32_t* addr) {
     int32_t oldValue;
     do {
         oldValue = *addr;
@@ -101,7 +125,12 @@ int32_t android_atomic_swap(int32_t value, volatile int32_t* addr) {
     return oldValue;
 }
 
-int android_atomic_cmpxchg(int32_t oldvalue, int32_t newvalue,
+int android_atomic_acquire_cmpxchg(int32_t oldvalue, int32_t newvalue,
+                           volatile int32_t* addr) {
+    return android_atomic_release_cmpxchg(oldValue, newValue, addr);
+}
+
+int android_atomic_release_cmpxchg(int32_t oldvalue, int32_t newvalue,
                            volatile int32_t* addr) {
     int result;
     pthread_mutex_t*  lock = SWAP_LOCK(addr);
@@ -118,8 +147,3 @@ int android_atomic_cmpxchg(int32_t oldvalue, int32_t newvalue,
     return result;
 }
 
-int android_atomic_acquire_cmpxchg(int32_t oldvalue, int32_t newvalue,
-                           volatile int32_t* addr) {
-    return android_atomic_cmpxchg(oldValue, newValue, addr);
-}
-