am 81542db7: am f761709a: am 1829b14c: am 18e754ee: Merge "Fix LP64 tombstone.cpp build failure."
* commit '81542db7c2cdf44803ba36be0f8cd76972790fc0':
diff --git a/include/cutils/atomic.h b/include/cutils/atomic.h
index 1787e34..b9b18c4 100644
--- a/include/cutils/atomic.h
+++ b/include/cutils/atomic.h
@@ -25,8 +25,20 @@
#endif
/*
- * A handful of basic atomic operations. The appropriate pthread
- * functions should be used instead of these whenever possible.
+ * A handful of basic atomic operations.
+ * THESE ARE HERE FOR LEGACY REASONS ONLY. AVOID.
+ *
+ * PREFERRED ALTERNATIVES:
+ * - Use C++/C/pthread locks/mutexes whenever there is not a
+ * convincing reason to do otherwise. Note that very clever and
+ * complicated, but correct, lock-free code is often slower than
+ * using locks, especially where nontrivial data structures
+ * are involved.
+ * - C11 stdatomic.h.
+ * - Where supported, C++11 std::atomic<T> .
+ *
+ * PLEASE STOP READING HERE UNLESS YOU ARE TRYING TO UNDERSTAND
+ * OR UPDATE OLD CODE.
*
* The "acquire" and "release" terms can be defined intuitively in terms
* of the placement of memory barriers in a simple lock implementation:
@@ -74,6 +86,17 @@
/*
* Perform an atomic load with "acquire" or "release" ordering.
*
+ * Note that the notion of a "release" ordering for a load does not
+ * really fit into the C11 or C++11 memory model. The extra ordering
+ * is normally observable only by code using memory_order_relaxed
+ * atomics, or data races. In the rare cases in which such ordering
+ * is called for, use memory_order_relaxed atomics and a leading
+ * atomic_thread_fence (typically with memory_order_acquire,
+ * not memory_order_release!) instead. If you do not understand
+ * this comment, you are in the vast majority, and should not be
+ * using release loads or replacing them with anything other than
+ * locks or default sequentially consistent atomics.
+ *
* This is only necessary if you need the memory barrier. A 32-bit read
* from a 32-bit aligned address is atomic on all supported platforms.
*/
@@ -88,6 +111,14 @@
/*
* Perform an atomic store with "acquire" or "release" ordering.
*
+ * Note that the notion of a "acquire" ordering for a store does not
+ * really fit into the C11 or C++11 memory model. The extra ordering
+ * is normally observable only by code using memory_order_relaxed
+ * atomics, or data races. In the rare cases in which such ordering
+ * is called for, use memory_order_relaxed atomics and a trailing
+ * atomic_thread_fence (typically with memory_order_release,
+ * not memory_order_acquire!) instead.
+ *
* This is only necessary if you need the memory barrier. A 32-bit write
* to a 32-bit aligned address is atomic on all supported platforms.
*/
diff --git a/rootdir/init.rc b/rootdir/init.rc
index b3ccae1..1bbc7ab 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -255,6 +255,7 @@
mkdir /data/misc/bluetooth 0770 system system
mkdir /data/misc/keystore 0700 keystore keystore
mkdir /data/misc/keychain 0771 system system
+ mkdir /data/misc/net 0750 root shell
mkdir /data/misc/radio 0770 system radio
mkdir /data/misc/sms 0770 system radio
mkdir /data/misc/zoneinfo 0775 system system