From 8bd30b3cf351377adbbe71a1e9b4df97eb47acda Mon Sep 17 00:00:00 2001 From: Todd Poynor Date: Mon, 26 Jun 2017 14:34:38 -0700 Subject: [PATCH] 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 --- healthd/BatteryPropertiesRegistrar.cpp | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/healthd/BatteryPropertiesRegistrar.cpp b/healthd/BatteryPropertiesRegistrar.cpp index 523e1f136..e51a06d5e 100644 --- a/healthd/BatteryPropertiesRegistrar.cpp +++ b/healthd/BatteryPropertiesRegistrar.cpp @@ -36,9 +36,19 @@ void BatteryPropertiesRegistrar::publish( } 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 > 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); } }