bionic: add __system_property_area_serial()
Adds a new _internal_ function. Provide a global serial number to
support more efficient private caching algorithms. This allows
to skip re-running the __system_property_find() call on misses until
there is a global change in the properties. This call is a read
barrier, the property data to be read following this call will be
read sequentially and up to date.
Bug: 19544788
Change-Id: I58e6a92baa0f3e8e7b9ec79b10af6d56407dab48
diff --git a/libc/bionic/system_properties.cpp b/libc/bionic/system_properties.cpp
index aae99b1..c436a16 100644
--- a/libc/bionic/system_properties.cpp
+++ b/libc/bionic/system_properties.cpp
@@ -598,6 +598,16 @@
return map_prop_area_rw();
}
+unsigned int __system_property_area_serial()
+{
+ prop_area *pa = __system_property_area__;
+ if (!pa) {
+ return -1;
+ }
+ // Make sure this read fulfilled before __system_property_serial
+ return atomic_load_explicit(&(pa->serial), memory_order_acquire);
+}
+
const prop_info *__system_property_find(const char *name)
{
if (__predict_false(compat_mode)) {