replicant-frameworks_native/services/surfaceflinger/EventThread.cpp
Mathias Agopian 7d88647473 SF could get stuck waiting for vsync when turning the screen off
When turning the screen off we could have 2 waiters on the
vsync condition: The main vsync waiter as well as one in
onScreenReleased(). We were only signaling the condition though,
so it it would be possible to wake onScreenReleased() without waking
the main vsync thread which would then be stuck in .wait().

We fix this by just using broadcast() when receiving a vsync event.

We also add a broadcast() to signal when the state of
mUseSoftwareVSync changes.  This is important particularly for
the transition from hardware to software vsync because the main
vsync waiter might have observed mUseSoftwareVSync == false
and decided to block indefinitely pending a hardware vsync
signal that will never arrive.

Removed a potentially deadlocking wait for a signal in
onScreenReleased().  The function was trying to wait for the last
vsync event from the hardware to be delivered to clients but there
was no guarantee that another thread would signal it to wake up
again afterwards.  (As far as I can tell, the only other other
thread that might wake it up at this point would be a client
application issuing a vsync request.)  We don't really need to wait
here anyhow.  It's enough to set the mUseSoftwareVSync flag,
wake up the thread loop and go.  If there was a pending vsync
timestamp from the hardware, then the thread loop will grab
it and use it then start software vsync on the next iteration.

Bug: 6672102
Change-Id: I7c6abc23bb021d1dfc94f101bd3ce18e3a81a73e
2012-06-15 14:59:31 -07:00

326 lines
11 KiB
C++

/*
* Copyright (C) 2011 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.
*/
#define ATRACE_TAG ATRACE_TAG_GRAPHICS
#include <stdint.h>
#include <sys/types.h>
#include <gui/BitTube.h>
#include <gui/IDisplayEventConnection.h>
#include <gui/DisplayEventReceiver.h>
#include <utils/Errors.h>
#include <utils/Trace.h>
#include "DisplayHardware/DisplayHardware.h"
#include "EventThread.h"
#include "SurfaceFlinger.h"
// ---------------------------------------------------------------------------
namespace android {
// ---------------------------------------------------------------------------
EventThread::EventThread(const sp<SurfaceFlinger>& flinger)
: mFlinger(flinger),
mHw(flinger->graphicPlane(0).editDisplayHardware()),
mLastVSyncTimestamp(0),
mVSyncTimestamp(0),
mUseSoftwareVSync(false),
mDeliveredEvents(0),
mDebugVsyncEnabled(false)
{
}
void EventThread::onFirstRef() {
mHw.setVSyncHandler(this);
run("EventThread", PRIORITY_URGENT_DISPLAY + PRIORITY_MORE_FAVORABLE);
}
sp<EventThread::Connection> EventThread::createEventConnection() const {
return new Connection(const_cast<EventThread*>(this));
}
status_t EventThread::registerDisplayEventConnection(
const sp<EventThread::Connection>& connection) {
Mutex::Autolock _l(mLock);
mDisplayEventConnections.add(connection);
mCondition.broadcast();
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);
mDisplayEventConnections.remove(connection);
}
void EventThread::setVsyncRate(uint32_t count,
const sp<EventThread::Connection>& connection) {
if (int32_t(count) >= 0) { // server must protect against bad params
Mutex::Autolock _l(mLock);
const int32_t new_count = (count == 0) ? -1 : count;
if (connection->count != new_count) {
connection->count = new_count;
mCondition.broadcast();
}
}
}
void EventThread::requestNextVsync(
const sp<EventThread::Connection>& connection) {
Mutex::Autolock _l(mLock);
if (connection->count < 0) {
connection->count = 0;
mCondition.broadcast();
}
}
void EventThread::onScreenReleased() {
Mutex::Autolock _l(mLock);
if (!mUseSoftwareVSync) {
// disable reliance on h/w vsync
mUseSoftwareVSync = true;
mCondition.broadcast();
}
}
void EventThread::onScreenAcquired() {
Mutex::Autolock _l(mLock);
if (mUseSoftwareVSync) {
// resume use of h/w vsync
mUseSoftwareVSync = false;
mCondition.broadcast();
}
}
void EventThread::onVSyncReceived(int, nsecs_t timestamp) {
Mutex::Autolock _l(mLock);
mVSyncTimestamp = timestamp;
mCondition.broadcast();
}
bool EventThread::threadLoop() {
nsecs_t timestamp;
DisplayEventReceiver::Event vsync;
Vector< wp<EventThread::Connection> > displayEventConnections;
do {
Mutex::Autolock _l(mLock);
do {
// latch VSYNC event if any
timestamp = mVSyncTimestamp;
mVSyncTimestamp = 0;
// check if we should be waiting for VSYNC events
bool waitForNextVsync = false;
size_t count = mDisplayEventConnections.size();
for (size_t i=0 ; i<count ; i++) {
sp<Connection> connection =
mDisplayEventConnections.itemAt(i).promote();
if (connection!=0 && connection->count >= 0) {
// at least one continuous mode or active one-shot event
waitForNextVsync = true;
break;
}
}
if (timestamp) {
if (!waitForNextVsync) {
// 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 (waitForNextVsync) {
// enable
enableVSyncLocked();
}
}
// wait for something to happen
if (mUseSoftwareVSync && waitForNextVsync) {
// 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);
}
} else {
mCondition.wait(mLock);
}
} while(true);
// process vsync event
mDeliveredEvents++;
mLastVSyncTimestamp = timestamp;
// now see if we still need to report this VSYNC event
const size_t count = mDisplayEventConnections.size();
for (size_t i=0 ; i<count ; i++) {
bool reportVsync = false;
sp<Connection> connection =
mDisplayEventConnections.itemAt(i).promote();
if (connection == 0)
continue;
const int32_t count = connection->count;
if (count >= 1) {
if (count==1 || (mDeliveredEvents % count) == 0) {
// continuous event, and time to report it
reportVsync = true;
}
} else if (count >= -1) {
if (count == 0) {
// fired this time around
reportVsync = true;
}
connection->count--;
}
if (reportVsync) {
displayEventConnections.add(connection);
}
}
} while (!displayEventConnections.size());
// dispatch vsync events to listeners...
vsync.header.type = DisplayEventReceiver::DISPLAY_EVENT_VSYNC;
vsync.header.timestamp = timestamp;
vsync.vsync.count = mDeliveredEvents;
const size_t count = displayEventConnections.size();
for (size_t i=0 ; i<count ; i++) {
sp<Connection> conn(displayEventConnections[i].promote());
// make sure the connection didn't die
if (conn != NULL) {
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(displayEventConnections[i]);
}
} else {
// somehow the connection is dead, but we still have it in our list
// just clean the list.
removeDisplayEventConnection(displayEventConnections[i]);
}
}
// clear all our references without holding mLock
displayEventConnections.clear();
return true;
}
void EventThread::enableVSyncLocked() {
if (!mUseSoftwareVSync) {
// never enable h/w VSYNC when screen is off
mHw.eventControl(DisplayHardware::EVENT_VSYNC, true);
}
mDebugVsyncEnabled = true;
}
void EventThread::disableVSyncLocked() {
mHw.eventControl(DisplayHardware::EVENT_VSYNC, false);
mDebugVsyncEnabled = false;
}
status_t EventThread::readyToRun() {
ALOGI("EventThread ready to run.");
return NO_ERROR;
}
void EventThread::dump(String8& result, char* buffer, size_t SIZE) const {
Mutex::Autolock _l(mLock);
result.appendFormat("VSYNC state: %s\n",
mDebugVsyncEnabled?"enabled":"disabled");
result.appendFormat(" soft-vsync: %s\n",
mUseSoftwareVSync?"enabled":"disabled");
result.appendFormat(" numListeners=%u,\n events-delivered: %u\n",
mDisplayEventConnections.size(), mDeliveredEvents);
for (size_t i=0 ; i<mDisplayEventConnections.size() ; i++) {
sp<Connection> connection =
mDisplayEventConnections.itemAt(i).promote();
result.appendFormat(" %p: count=%d\n",
connection.get(), connection!=NULL ? connection->count : 0);
}
}
// ---------------------------------------------------------------------------
EventThread::Connection::Connection(
const sp<EventThread>& eventThread)
: count(-1), mEventThread(eventThread), mChannel(new BitTube())
{
}
EventThread::Connection::~Connection() {
mEventThread->unregisterDisplayEventConnection(this);
}
void EventThread::Connection::onFirstRef() {
// NOTE: mEventThread doesn't hold a strong reference on us
mEventThread->registerDisplayEventConnection(this);
}
sp<BitTube> EventThread::Connection::getDataChannel() const {
return mChannel;
}
void EventThread::Connection::setVsyncRate(uint32_t count) {
mEventThread->setVsyncRate(count, this);
}
void EventThread::Connection::requestNextVsync() {
mEventThread->requestNextVsync(this);
}
status_t EventThread::Connection::postEvent(
const DisplayEventReceiver::Event& event) {
ssize_t size = DisplayEventReceiver::sendEvents(mChannel, &event, 1);
return size < 0 ? status_t(size) : status_t(NO_ERROR);
}
// ---------------------------------------------------------------------------
}; // namespace android