platform_system_core/healthd/BatteryPropertiesRegistrar.cpp
Todd Poynor 8bd30b3cf3 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
2017-06-29 22:25:40 +00:00

118 lines
4 KiB
C++

/*
* Copyright (C) 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "BatteryPropertiesRegistrar.h"
#include <batteryservice/BatteryService.h>
#include <batteryservice/IBatteryPropertiesListener.h>
#include <batteryservice/IBatteryPropertiesRegistrar.h>
#include <binder/IPCThreadState.h>
#include <binder/IServiceManager.h>
#include <binder/PermissionCache.h>
#include <private/android_filesystem_config.h>
#include <utils/Errors.h>
#include <utils/Mutex.h>
#include <utils/String16.h>
#include <healthd/healthd.h>
namespace android {
void BatteryPropertiesRegistrar::publish(
const sp<BatteryPropertiesRegistrar>& service) {
defaultServiceManager()->addService(String16("batteryproperties"), service);
}
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);
listenersCopy = mListeners;
}
for (size_t i = 0; i < listenersCopy.size(); i++) {
listenersCopy[i]->batteryPropertiesChanged(props);
}
}
void BatteryPropertiesRegistrar::registerListener(const sp<IBatteryPropertiesListener>& listener) {
{
if (listener == NULL)
return;
Mutex::Autolock _l(mRegistrationLock);
// check whether this is a duplicate
for (size_t i = 0; i < mListeners.size(); i++) {
if (IInterface::asBinder(mListeners[i]) == IInterface::asBinder(listener)) {
return;
}
}
mListeners.add(listener);
IInterface::asBinder(listener)->linkToDeath(this);
}
healthd_battery_update();
}
void BatteryPropertiesRegistrar::unregisterListener(const sp<IBatteryPropertiesListener>& listener) {
if (listener == NULL)
return;
Mutex::Autolock _l(mRegistrationLock);
for (size_t i = 0; i < mListeners.size(); i++) {
if (IInterface::asBinder(mListeners[i]) == IInterface::asBinder(listener)) {
IInterface::asBinder(mListeners[i])->unlinkToDeath(this);
mListeners.removeAt(i);
break;
}
}
}
status_t BatteryPropertiesRegistrar::getProperty(int id, struct BatteryProperty *val) {
return healthd_get_property(id, val);
}
void BatteryPropertiesRegistrar::scheduleUpdate() {
healthd_battery_update();
}
status_t BatteryPropertiesRegistrar::dump(int fd, const Vector<String16>& /*args*/) {
IPCThreadState* self = IPCThreadState::self();
const int pid = self->getCallingPid();
const int uid = self->getCallingUid();
if ((uid != AID_SHELL) &&
!PermissionCache::checkPermission(
String16("android.permission.DUMP"), pid, uid))
return PERMISSION_DENIED;
healthd_dump_battery_state(fd);
return OK;
}
void BatteryPropertiesRegistrar::binderDied(const wp<IBinder>& who) {
Mutex::Autolock _l(mRegistrationLock);
for (size_t i = 0; i < mListeners.size(); i++) {
if (IInterface::asBinder(mListeners[i]) == who) {
mListeners.removeAt(i);
break;
}
}
}
} // namespace android