healthd: notify listeners using local copy of list, drop lock
Binder currently may service an incoming oneway transaction whenever
an outbound oneway call is made (if there is already a pending
incoming oneway call waiting). The unexpected nested method call
blocks forever on a recursive mutex acquire because healthd is single-
threaded. The binder behavior is considered a bug and may change in
the future. For now, work around this in healthd.
Make a local copy of the listeners list, then drop the lock and
perform the outbound calls on the local copy of the list.
Bug: 38201220
Test: Marlin with modified client calling scheduleUpdate() repeatedly
Change-Id: If35c2847556245921e2aff808ff747bb60356811
diff --git a/healthd/BatteryPropertiesRegistrar.cpp b/healthd/BatteryPropertiesRegistrar.cpp
index 523e1f1..e51a06d 100644
--- a/healthd/BatteryPropertiesRegistrar.cpp
+++ b/healthd/BatteryPropertiesRegistrar.cpp
@@ -36,9 +36,19 @@
}
void BatteryPropertiesRegistrar::notifyListeners(const struct BatteryProperties& props) {
- Mutex::Autolock _l(mRegistrationLock);
- for (size_t i = 0; i < mListeners.size(); i++) {
- mListeners[i]->batteryPropertiesChanged(props);
+ Vector<sp<IBatteryPropertiesListener> > listenersCopy;
+
+ // Binder currently may service an incoming oneway transaction whenever an
+ // outbound oneway call is made (if there is already a pending incoming
+ // oneway call waiting). This is considered a bug and may change in the
+ // future. For now, avoid recursive mutex lock while making outbound
+ // calls by making a local copy of the current list of listeners.
+ {
+ Mutex::Autolock _l(mRegistrationLock);
+ listenersCopy = mListeners;
+ }
+ for (size_t i = 0; i < listenersCopy.size(); i++) {
+ listenersCopy[i]->batteryPropertiesChanged(props);
}
}
