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fix various issues in SF's EventThread 

- one issues caused most timestamps to be reported as 0
- on rare occasions an uninitialized variable could be used
- vsync counts per connection were accessed unthreadsafely

we now have 2 lists of connections in the main loop, one just
keeps a list of strong refs to the connections because once
we have a strong ref we're not allowed to release it while
holding the lock.

the 2nd list holds the connections that have a vsync event to
be reported. all the calculations are made with the lock held.

Change-Id: Iacfad3745b05df79d9ece3719bd4c34ddbfd5b83
This commit is contained in:
Mathias Agopian 2012-08-20 20:07:34 -07:00
parent 1648d4c13b
commit a4cb35a286
2 changed files with 51 additions and 51 deletions
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101
services/surfaceflinger/EventThread.cpp
View File

@ -19,6 +19,8 @@
#include <stdint.h>
#include <sys/types.h>
#include <cutils/compiler.h>
#include <gui/BitTube.h>
#include <gui/IDisplayEventConnection.h>
#include <gui/DisplayEventReceiver.h>
@ -123,35 +125,53 @@ bool EventThread::threadLoop() {
nsecs_t timestamp;
size_t vsyncCount;
size_t activeEvents;
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;
// check if we should be waiting for VSYNC events
activeEvents = 0;
bool waitForNextVsync = false;
// 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) {
// at least one continuous mode or active one-shot event
waitForNextVsync = true;
activeEvents++;
break;
// 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) {
if (!waitForNextVsync) {
// 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();
@ -164,14 +184,14 @@ bool EventThread::threadLoop() {
// we'll wait to receive the event and we'll
// reevaluate whether we need to dispatch it and/or
// disable VSYNC events then.
if (waitForNextVsync) {
if (waitForVSync) {
// enable
enableVSyncLocked();
}
}
// wait for something to happen
if (mUseSoftwareVSync && waitForNextVsync) {
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
@ -180,54 +200,35 @@ bool EventThread::threadLoop() {
mVSyncCount++;
}
} else {
mCondition.wait(mLock);
if (!timestamp || signalConnections.isEmpty()) {
// This is where we spend most of our time, waiting
// for a vsync events and registered clients
mCondition.wait(mLock);
}
}
vsyncCount = mVSyncCount;
} while (!activeConnections.size());
if (!activeEvents) {
// no events to return. start over.
// (here we make sure to exit the scope of this function
// so that we release our Connection references)
return true;
}
} while (!timestamp || signalConnections.isEmpty());
// dispatch vsync events to listeners...
vsync.header.type = DisplayEventReceiver::DISPLAY_EVENT_VSYNC;
vsync.header.timestamp = timestamp;
vsync.vsync.count = vsyncCount;
const size_t count = activeConnections.size();
const size_t count = signalConnections.size();
for (size_t i=0 ; i<count ; i++) {
const sp<Connection>& conn(activeConnections[i]);
const sp<Connection>& conn(signalConnections[i]);
// now see if we still need to report this VSYNC event
const int32_t vcount = conn->count;
if (vcount >= 0) {
bool reportVsync = false;
if (vcount == 0) {
// fired this time around
conn->count = -1;
reportVsync = true;
} else if (vcount == 1 || (vsyncCount % vcount) == 0) {
// continuous event, and time to report it
reportVsync = true;
}
if (reportVsync) {
status_t err = conn->postEvent(vsync);
if (err == -EAGAIN || err == -EWOULDBLOCK) {
// The destination doesn't accept events anymore, it's probably
// full. For now, we just drop the events on the floor.
// Note that some events cannot be dropped and would have to be
// re-sent later. Right-now we don't have the ability to do
// this, but it doesn't matter for VSYNC.
} else if (err < 0) {
// handle any other error on the pipe as fatal. the only
// reasonable thing to do is to clean-up this connection.
// The most common error we'll get here is -EPIPE.
removeDisplayEventConnection(activeConnections[i]);
}
}
status_t err = conn->postEvent(vsync);
if (err == -EAGAIN || err == -EWOULDBLOCK) {
// The destination doesn't accept events anymore, it's probably
// full. For now, we just drop the events on the floor.
// Note that some events cannot be dropped and would have to be
// re-sent later. Right-now we don't have the ability to do
// this, but it doesn't matter for VSYNC.
} else if (err < 0) {
// handle any other error on the pipe as fatal. the only
// reasonable thing to do is to clean-up this connection.
// The most common error we'll get here is -EPIPE.
removeDisplayEventConnection(signalConnections[i]);
}
}

1
services/surfaceflinger/EventThread.h
View File

@ -47,7 +47,6 @@ class EventThread : public Thread {
// count >= 1 : continuous event. count is the vsync rate
// count == 0 : one-shot event that has not fired
// count ==-1 : one-shot event that fired this round / disabled
// count ==-2 : one-shot event that fired the round before
int32_t count;
private: