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simplify further vsync handling 

- we now clean-up "dead" connection in the main loop,
this entirely avoid the problem with the side effects of
releasing strong references. We now only hold on to strong
reference for the connection we will signal.

- also simplify how we build the list of "ready" connections, by
only adding them to the list when we did receive a vsync event

Change-Id: I2a84da431320a2af8e8a93e07622a1d258236f43
This commit is contained in:
Mathias Agopian 2012-08-21 15:47:28 -07:00
parent bc46e0ad86
commit f6bbd44a23
2 changed files with 91 additions and 98 deletions
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185
services/surfaceflinger/EventThread.cpp
View File

@ -60,14 +60,6 @@ status_t EventThread::registerDisplayEventConnection(
return NO_ERROR;
}
status_t EventThread::unregisterDisplayEventConnection(
const wp<EventThread::Connection>& connection) {
Mutex::Autolock _l(mLock);
mDisplayEventConnections.remove(connection);
mCondition.broadcast();
return NO_ERROR;
}
void EventThread::removeDisplayEventConnection(
const wp<EventThread::Connection>& connection) {
Mutex::Autolock _l(mLock);
@ -122,97 +114,11 @@ void EventThread::onVSyncReceived(int, nsecs_t timestamp) {
}
bool EventThread::threadLoop() {
nsecs_t timestamp;
size_t vsyncCount;
DisplayEventReceiver::Event vsync;
Vector< sp<EventThread::Connection> > activeConnections;
Vector< sp<EventThread::Connection> > signalConnections;
do {
// release our references
signalConnections.clear();
activeConnections.clear();
Mutex::Autolock _l(mLock);
// latch VSYNC event if any
bool waitForVSync = false;
vsyncCount = mVSyncCount;
timestamp = mVSyncTimestamp;
mVSyncTimestamp = 0;
// find out connections waiting for VSYNC events
size_t count = mDisplayEventConnections.size();
for (size_t i=0 ; i<count ; i++) {
sp<Connection> connection(mDisplayEventConnections[i].promote());
if (connection != NULL) {
activeConnections.add(connection);
if (connection->count >= 0) {
// we need vsync events because at least
// one connection is waiting for it
waitForVSync = true;
if (connection->count == 0) {
// fired this time around
if (timestamp) {
// only "consume" this event if we're going to
// report it
connection->count = -1;
}
signalConnections.add(connection);
} else if (connection->count == 1 ||
(vsyncCount % connection->count) == 0) {
// continuous event, and time to report it
signalConnections.add(connection);
}
}
}
}
if (timestamp) {
// we have a vsync event we can dispatch
if (!waitForVSync) {
// we received a VSYNC but we have no clients
// don't report it, and disable VSYNC events
disableVSyncLocked();
} else {
// report VSYNC event
break;
}
} else {
// never disable VSYNC events immediately, instead
// we'll wait to receive the event and we'll
// reevaluate whether we need to dispatch it and/or
// disable VSYNC events then.
if (waitForVSync) {
// enable
enableVSyncLocked();
}
}
// wait for something to happen
if (CC_UNLIKELY(mUseSoftwareVSync && waitForVSync)) {
// h/w vsync cannot be used (screen is off), so we use
// a timeout instead. it doesn't matter how imprecise this
// is, we just need to make sure to serve the clients
if (mCondition.waitRelative(mLock, ms2ns(16)) == TIMED_OUT) {
mVSyncTimestamp = systemTime(SYSTEM_TIME_MONOTONIC);
mVSyncCount++;
}
} else {
if (!timestamp || signalConnections.isEmpty()) {
// This is where we spend most of our time, waiting
// for a vsync events and registered clients
mCondition.wait(mLock);
}
}
} while (!timestamp || signalConnections.isEmpty());
signalConnections = waitForEvent(&vsync);
// dispatch vsync events to listeners...
vsync.header.type = DisplayEventReceiver::DISPLAY_EVENT_VSYNC;
vsync.header.timestamp = timestamp;
vsync.vsync.count = vsyncCount;
const size_t count = signalConnections.size();
for (size_t i=0 ; i<count ; i++) {
const sp<Connection>& conn(signalConnections[i]);
@ -231,10 +137,94 @@ bool EventThread::threadLoop() {
removeDisplayEventConnection(signalConnections[i]);
}
}
return true;
}
Vector< sp<EventThread::Connection> > EventThread::waitForEvent(
DisplayEventReceiver::Event* event)
{
Mutex::Autolock _l(mLock);
size_t vsyncCount;
nsecs_t timestamp;
Vector< sp<EventThread::Connection> > signalConnections;
do {
// latch VSYNC event if any
bool waitForVSync = false;
vsyncCount = mVSyncCount;
timestamp = mVSyncTimestamp;
mVSyncTimestamp = 0;
// find out connections waiting for events
size_t count = mDisplayEventConnections.size();
for (size_t i=0 ; i<count ; i++) {
sp<Connection> connection(mDisplayEventConnections[i].promote());
if (connection != NULL) {
if (connection->count >= 0) {
// we need vsync events because at least
// one connection is waiting for it
waitForVSync = true;
if (timestamp) {
// we consume the event only if it's time
// (ie: we received a vsync event)
if (connection->count == 0) {
// fired this time around
connection->count = -1;
signalConnections.add(connection);
} else if (connection->count == 1 ||
(vsyncCount % connection->count) == 0) {
// continuous event, and time to report it
signalConnections.add(connection);
}
}
}
} else {
// we couldn't promote this reference, the connection has
// died, so clean-up!
mDisplayEventConnections.removeAt(i);
--i; --count;
}
}
// Here we figure out if we need to enable or disable vsyncs
if (timestamp && !waitForVSync) {
// we received a VSYNC but we have no clients
// don't report it, and disable VSYNC events
disableVSyncLocked();
} else if (!timestamp && waitForVSync) {
enableVSyncLocked();
}
// note: !timestamp implies signalConnections.isEmpty()
if (!timestamp) {
// wait for something to happen
if (CC_UNLIKELY(mUseSoftwareVSync && waitForVSync)) {
// h/w vsync cannot be used (screen is off), so we use
// a timeout instead. it doesn't matter how imprecise this
// is, we just need to make sure to serve the clients
if (mCondition.waitRelative(mLock, ms2ns(16)) == TIMED_OUT) {
mVSyncTimestamp = systemTime(SYSTEM_TIME_MONOTONIC);
mVSyncCount++;
}
} else {
// This is where we spend most of our time, waiting
// for a vsync events and registered clients
mCondition.wait(mLock);
}
}
} while (signalConnections.isEmpty());
// here we're guaranteed to have a timestamp and some connections to signal
// dispatch vsync events to listeners...
event->header.type = DisplayEventReceiver::DISPLAY_EVENT_VSYNC;
event->header.timestamp = timestamp;
event->vsync.count = vsyncCount;
return signalConnections;
}
void EventThread::enableVSyncLocked() {
if (!mUseSoftwareVSync) {
// never enable h/w VSYNC when screen is off
@ -280,7 +270,8 @@ EventThread::Connection::Connection(
}
EventThread::Connection::~Connection() {
mEventThread->unregisterDisplayEventConnection(this);
// do nothing here -- clean-up will happen automatically
// when the main thread wakes up
}
void EventThread::Connection::onFirstRef() {

4
services/surfaceflinger/EventThread.h
View File

@ -65,7 +65,6 @@ public:
sp<Connection> createEventConnection() const;
status_t registerDisplayEventConnection(const sp<Connection>& connection);
status_t unregisterDisplayEventConnection(const wp<Connection>& connection);
void setVsyncRate(uint32_t count, const sp<Connection>& connection);
void requestNextVsync(const sp<Connection>& connection);
@ -79,6 +78,9 @@ public:
// called when receiving a vsync event
void onVSyncReceived(int display, nsecs_t timestamp);
Vector< sp<EventThread::Connection> > waitForEvent(
DisplayEventReceiver::Event* event);
void dump(String8& result, char* buffer, size_t SIZE) const;
private: