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Commit fd683700 authored by Todd Poynor's avatar Todd Poynor
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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
parent 4f5f558d
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+13 −3
Original line number Diff line number Diff line
@@ -36,9 +36,19 @@ void BatteryPropertiesRegistrar::publish(
}

void BatteryPropertiesRegistrar::notifyListeners(const struct BatteryProperties& 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);
    for (size_t i = 0; i < mListeners.size(); i++) {
        mListeners[i]->batteryPropertiesChanged(props);
        listenersCopy = mListeners;
    }
    for (size_t i = 0; i < listenersCopy.size(); i++) {
        listenersCopy[i]->batteryPropertiesChanged(props);
    }
}