Fix deadlock in SF.
problem was that we were acquiring a strong reference on Connection object with a lock held, when those got out of scope (lock still held) their dtor could be called if all other refs had dropped, the dtor would acquire the lock again to remove the Connection from the main list. boom. we rearange the code so this doesn't happen. Bug: 6942208 Change-Id: I0a0ebabce2842d29d60d645b64aac2f26640e59b
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2c7eb92b63
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@ -36,10 +36,9 @@ namespace android {
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EventThread::EventThread(const sp<SurfaceFlinger>& flinger)
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: mFlinger(flinger),
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mLastVSyncTimestamp(0),
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mVSyncTimestamp(0),
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mUseSoftwareVSync(false),
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mDeliveredEvents(0),
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mVSyncCount(0),
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mDebugVsyncEnabled(false) {
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}
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@ -116,34 +115,40 @@ void EventThread::onScreenAcquired() {
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void EventThread::onVSyncReceived(int, nsecs_t timestamp) {
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Mutex::Autolock _l(mLock);
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mVSyncTimestamp = timestamp;
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mVSyncCount++;
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mCondition.broadcast();
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}
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bool EventThread::threadLoop() {
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nsecs_t timestamp;
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size_t vsyncCount;
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size_t activeEvents;
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DisplayEventReceiver::Event vsync;
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Vector< wp<EventThread::Connection> > displayEventConnections;
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Vector< sp<EventThread::Connection> > activeConnections;
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do {
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Mutex::Autolock _l(mLock);
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do {
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// latch VSYNC event if any
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timestamp = mVSyncTimestamp;
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mVSyncTimestamp = 0;
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// check if we should be waiting for VSYNC events
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activeEvents = 0;
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bool waitForNextVsync = false;
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size_t count = mDisplayEventConnections.size();
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for (size_t i=0 ; i<count ; i++) {
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sp<Connection> connection =
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mDisplayEventConnections.itemAt(i).promote();
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if (connection!=0 && connection->count >= 0) {
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sp<Connection> connection(mDisplayEventConnections[i].promote());
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if (connection != NULL) {
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activeConnections.add(connection);
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if (connection->count >= 0) {
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// at least one continuous mode or active one-shot event
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waitForNextVsync = true;
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activeEvents++;
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break;
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}
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}
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}
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if (timestamp) {
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if (!waitForNextVsync) {
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@ -172,54 +177,43 @@ bool EventThread::threadLoop() {
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// is, we just need to make sure to serve the clients
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if (mCondition.waitRelative(mLock, ms2ns(16)) == TIMED_OUT) {
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mVSyncTimestamp = systemTime(SYSTEM_TIME_MONOTONIC);
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mVSyncCount++;
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}
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} else {
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mCondition.wait(mLock);
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}
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} while(true);
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vsyncCount = mVSyncCount;
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} while (!activeConnections.size());
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// process vsync event
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mDeliveredEvents++;
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mLastVSyncTimestamp = timestamp;
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// now see if we still need to report this VSYNC event
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const size_t count = mDisplayEventConnections.size();
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for (size_t i=0 ; i<count ; i++) {
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bool reportVsync = false;
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sp<Connection> connection =
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mDisplayEventConnections.itemAt(i).promote();
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if (connection == 0)
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continue;
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const int32_t count = connection->count;
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if (count >= 1) {
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if (count==1 || (mDeliveredEvents % count) == 0) {
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// continuous event, and time to report it
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reportVsync = true;
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if (!activeEvents) {
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// no events to return. start over.
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// (here we make sure to exit the scope of this function
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// so that we release our Connection references)
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return true;
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}
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} else if (count >= -1) {
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if (count == 0) {
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// fired this time around
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reportVsync = true;
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}
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connection->count--;
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}
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if (reportVsync) {
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displayEventConnections.add(connection);
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}
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}
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} while (!displayEventConnections.size());
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// dispatch vsync events to listeners...
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vsync.header.type = DisplayEventReceiver::DISPLAY_EVENT_VSYNC;
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vsync.header.timestamp = timestamp;
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vsync.vsync.count = mDeliveredEvents;
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vsync.vsync.count = vsyncCount;
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const size_t count = displayEventConnections.size();
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const size_t count = activeConnections.size();
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for (size_t i=0 ; i<count ; i++) {
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sp<Connection> conn(displayEventConnections[i].promote());
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// make sure the connection didn't die
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if (conn != NULL) {
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const sp<Connection>& conn(activeConnections[i]);
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// now see if we still need to report this VSYNC event
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const int32_t vcount = conn->count;
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if (vcount >= 0) {
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bool reportVsync = false;
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if (vcount == 0) {
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// fired this time around
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conn->count = -1;
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reportVsync = true;
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} else if (vcount == 1 || (vsyncCount % vcount) == 0) {
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// continuous event, and time to report it
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reportVsync = true;
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}
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if (reportVsync) {
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status_t err = conn->postEvent(vsync);
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if (err == -EAGAIN || err == -EWOULDBLOCK) {
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// The destination doesn't accept events anymore, it's probably
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@ -231,17 +225,11 @@ bool EventThread::threadLoop() {
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// handle any other error on the pipe as fatal. the only
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// reasonable thing to do is to clean-up this connection.
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// The most common error we'll get here is -EPIPE.
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removeDisplayEventConnection(displayEventConnections[i]);
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}
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} else {
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// somehow the connection is dead, but we still have it in our list
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// just clean the list.
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removeDisplayEventConnection(displayEventConnections[i]);
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removeDisplayEventConnection(activeConnections[i]);
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}
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}
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}
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}
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// clear all our references without holding mLock
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displayEventConnections.clear();
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return true;
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}
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@ -273,7 +261,7 @@ void EventThread::dump(String8& result, char* buffer, size_t SIZE) const {
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result.appendFormat(" soft-vsync: %s\n",
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mUseSoftwareVSync?"enabled":"disabled");
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result.appendFormat(" numListeners=%u,\n events-delivered: %u\n",
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mDisplayEventConnections.size(), mDeliveredEvents);
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mDisplayEventConnections.size(), mVSyncCount);
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for (size_t i=0 ; i<mDisplayEventConnections.size() ; i++) {
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sp<Connection> connection =
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mDisplayEventConnections.itemAt(i).promote();
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@ -100,12 +100,9 @@ private:
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// protected by mLock
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SortedVector< wp<Connection> > mDisplayEventConnections;
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nsecs_t mLastVSyncTimestamp;
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nsecs_t mVSyncTimestamp;
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bool mUseSoftwareVSync;
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// main thread only
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size_t mDeliveredEvents;
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size_t mVSyncCount;
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// for debugging
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bool mDebugVsyncEnabled;
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