//
// Copyright 2010 The Android Open Source Project
//
// A looper implementation based on epoll().
//
#define LOG_TAG "Looper"
//#define LOG_NDEBUG 0
// Debugs poll and wake interactions.
#define DEBUG_POLL_AND_WAKE 0
// Debugs callback registration and invocation.
#define DEBUG_CALLBACKS 0
#include <cutils/log.h>
#include <utils/Looper.h>
#include <utils/Timers.h>
#include <unistd.h>
#include <fcntl.h>
#include <limits.h>
namespace android {
// --- WeakMessageHandler ---
WeakMessageHandler::WeakMessageHandler(const wp<MessageHandler>& handler) :
mHandler(handler) {
}
void WeakMessageHandler::handleMessage(const Message& message) {
sp<MessageHandler> handler = mHandler.promote();
if (handler != NULL) {
handler->handleMessage(message);
}
}
// --- Looper ---
#ifdef LOOPER_USES_EPOLL
// Hint for number of file descriptors to be associated with the epoll instance.
static const int EPOLL_SIZE_HINT = 8;
// Maximum number of file descriptors for which to retrieve poll events each iteration.
static const int EPOLL_MAX_EVENTS = 16;
#endif
static pthread_once_t gTLSOnce = PTHREAD_ONCE_INIT;
static pthread_key_t gTLSKey = 0;
Looper::Looper(bool allowNonCallbacks) :
mAllowNonCallbacks(allowNonCallbacks), mSendingMessage(false),
mResponseIndex(0), mNextMessageUptime(LLONG_MAX) {
int wakeFds[2];
int result = pipe(wakeFds);
LOG_ALWAYS_FATAL_IF(result != 0, "Could not create wake pipe. errno=%d", errno);
mWakeReadPipeFd = wakeFds[0];
mWakeWritePipeFd = wakeFds[1];
result = fcntl(mWakeReadPipeFd, F_SETFL, O_NONBLOCK);
LOG_ALWAYS_FATAL_IF(result != 0, "Could not make wake read pipe non-blocking. errno=%d",
errno);
result = fcntl(mWakeWritePipeFd, F_SETFL, O_NONBLOCK);
LOG_ALWAYS_FATAL_IF(result != 0, "Could not make wake write pipe non-blocking. errno=%d",
errno);
#ifdef LOOPER_USES_EPOLL
// Allocate the epoll instance and register the wake pipe.
mEpollFd = epoll_create(EPOLL_SIZE_HINT);
LOG_ALWAYS_FATAL_IF(mEpollFd < 0, "Could not create epoll instance. errno=%d", errno);
struct epoll_event eventItem;
memset(& eventItem, 0, sizeof(epoll_event)); // zero out unused members of data field union
eventItem.events = EPOLLIN;
eventItem.data.fd = mWakeReadPipeFd;
result = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, mWakeReadPipeFd, & eventItem);
LOG_ALWAYS_FATAL_IF(result != 0, "Could not add wake read pipe to epoll instance. errno=%d",
errno);
#else
// Add the wake pipe to the head of the request list with a null callback.
struct pollfd requestedFd;
requestedFd.fd = mWakeReadPipeFd;
requestedFd.events = POLLIN;
mRequestedFds.push(requestedFd);
Request request;
request.fd = mWakeReadPipeFd;
request.callback = NULL;
request.ident = 0;
request.data = NULL;
mRequests.push(request);
mPolling = false;
mWaiters = 0;
#endif
#ifdef LOOPER_STATISTICS
mPendingWakeTime = -1;
mPendingWakeCount = 0;
mSampledWakeCycles = 0;
mSampledWakeCountSum = 0;
mSampledWakeLatencySum = 0;
mSampledPolls = 0;
mSampledZeroPollCount = 0;
mSampledZeroPollLatencySum = 0;
mSampledTimeoutPollCount = 0;
mSampledTimeoutPollLatencySum = 0;
#endif
}
Looper::~Looper() {
close(mWakeReadPipeFd);
close(mWakeWritePipeFd);
#ifdef LOOPER_USES_EPOLL
close(mEpollFd);
#endif
}
void Looper::initTLSKey() {
int result = pthread_key_create(& gTLSKey, threadDestructor);
LOG_ALWAYS_FATAL_IF(result != 0, "Could not allocate TLS key.");
}
void Looper::threadDestructor(void *st) {
Looper* const self = static_cast<Looper*>(st);
if (self != NULL) {
self->decStrong((void*)threadDestructor);
}
}
void Looper::setForThread(const sp<Looper>& looper) {
sp<Looper> old = getForThread(); // also has side-effect of initializing TLS
if (looper != NULL) {
looper->incStrong((void*)threadDestructor);
}
pthread_setspecific(gTLSKey, looper.get());
if (old != NULL) {
old->decStrong((void*)threadDestructor);
}
}
sp<Looper> Looper::getForThread() {
int result = pthread_once(& gTLSOnce, initTLSKey);
LOG_ALWAYS_FATAL_IF(result != 0, "pthread_once failed");
return (Looper*)pthread_getspecific(gTLSKey);
}
sp<Looper> Looper::prepare(int opts) {
bool allowNonCallbacks = opts & ALOOPER_PREPARE_ALLOW_NON_CALLBACKS;
sp<Looper> looper = Looper::getForThread();
if (looper == NULL) {
looper = new Looper(allowNonCallbacks);
Looper::setForThread(looper);
}
if (looper->getAllowNonCallbacks() != allowNonCallbacks) {
LOGW("Looper already prepared for this thread with a different value for the "
"ALOOPER_PREPARE_ALLOW_NON_CALLBACKS option.");
}
return looper;
}
bool Looper::getAllowNonCallbacks() const {
return mAllowNonCallbacks;
}
int Looper::pollOnce(int timeoutMillis, int* outFd, int* outEvents, void** outData) {
int result = 0;
for (;;) {
while (mResponseIndex < mResponses.size()) {
const Response& response = mResponses.itemAt(mResponseIndex++);
ALooper_callbackFunc callback = response.request.callback;
if (!callback) {
int ident = response.request.ident;
int fd = response.request.fd;
int events = response.events;
void* data = response.request.data;
#if DEBUG_POLL_AND_WAKE
LOGD("%p ~ pollOnce - returning signalled identifier %d: "
"fd=%d, events=0x%x, data=%p",
this, ident, fd, events, data);
#endif
if (outFd != NULL) *outFd = fd;
if (outEvents != NULL) *outEvents = events;
if (outData != NULL) *outData = data;
return ident;
}
}
if (result != 0) {
#if DEBUG_POLL_AND_WAKE
LOGD("%p ~ pollOnce - returning result %d", this, result);
#endif
if (outFd != NULL) *outFd = 0;
if (outEvents != NULL) *outEvents = NULL;
if (outData != NULL) *outData = NULL;
return result;
}
result = pollInner(timeoutMillis);
}
}
int Looper::pollInner(int timeoutMillis) {
#if DEBUG_POLL_AND_WAKE
LOGD("%p ~ pollOnce - waiting: timeoutMillis=%d", this, timeoutMillis);
#endif
// Adjust the timeout based on when the next message is due.
if (timeoutMillis != 0 && mNextMessageUptime != LLONG_MAX) {
nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
int messageTimeoutMillis = toMillisecondTimeoutDelay(now, mNextMessageUptime);
if (messageTimeoutMillis >= 0
&& (timeoutMillis < 0 || messageTimeoutMillis < timeoutMillis)) {
timeoutMillis = messageTimeoutMillis;
}
#if DEBUG_POLL_AND_WAKE
LOGD("%p ~ pollOnce - next message in %lldns, adjusted timeout: timeoutMillis=%d",
this, mNextMessageUptime - now, timeoutMillis);
#endif
}
// Poll.
int result = ALOOPER_POLL_WAKE;
mResponses.clear();
mResponseIndex = 0;
#ifdef LOOPER_STATISTICS
nsecs_t pollStartTime = systemTime(SYSTEM_TIME_MONOTONIC);
#endif
#ifdef LOOPER_USES_EPOLL
struct epoll_event eventItems[EPOLL_MAX_EVENTS];
int eventCount = epoll_wait(mEpollFd, eventItems, EPOLL_MAX_EVENTS, timeoutMillis);
#else
// Wait for wakeAndLock() waiters to run then set mPolling to true.
mLock.lock();
while (mWaiters != 0) {
mResume.wait(mLock);
}
mPolling = true;
mLock.unlock();
size_t requestedCount = mRequestedFds.size();
int eventCount = poll(mRequestedFds.editArray(), requestedCount, timeoutMillis);
#endif
// Acquire lock.
mLock.lock();
// Check for poll error.
if (eventCount < 0) {
if (errno == EINTR) {
goto Done;
}
LOGW("Poll failed with an unexpected error, errno=%d", errno);
result = ALOOPER_POLL_ERROR;
goto Done;
}
// Check for poll timeout.
if (eventCount == 0) {
#if DEBUG_POLL_AND_WAKE
LOGD("%p ~ pollOnce - timeout", this);
#endif
result = ALOOPER_POLL_TIMEOUT;
goto Done;
}
// Handle all events.
#if DEBUG_POLL_AND_WAKE
LOGD("%p ~ pollOnce - handling events from %d fds", this, eventCount);
#endif
#ifdef LOOPER_USES_EPOLL
for (int i = 0; i < eventCount; i++) {
int fd = eventItems[i].data.fd;
uint32_t epollEvents = eventItems[i].events;
if (fd == mWakeReadPipeFd) {
if (epollEvents & EPOLLIN) {
awoken();
} else {
LOGW("Ignoring unexpected epoll events 0x%x on wake read pipe.", epollEvents);
}
} else {
ssize_t requestIndex = mRequests.indexOfKey(fd);
if (requestIndex >= 0) {
int events = 0;
if (epollEvents & EPOLLIN) events |= ALOOPER_EVENT_INPUT;
if (epollEvents & EPOLLOUT) events |= ALOOPER_EVENT_OUTPUT;
if (epollEvents & EPOLLERR) events |= ALOOPER_EVENT_ERROR;
if (epollEvents & EPOLLHUP) events |= ALOOPER_EVENT_HANGUP;
pushResponse(events, mRequests.valueAt(requestIndex));
} else {
LOGW("Ignoring unexpected epoll events 0x%x on fd %d that is "
"no longer registered.", epollEvents, fd);
}
}
}
Done: ;
#else
for (size_t i = 0; i < requestedCount; i++) {
const struct pollfd& requestedFd = mRequestedFds.itemAt(i);
short pollEvents = requestedFd.revents;
if (pollEvents) {
if (requestedFd.fd == mWakeReadPipeFd) {
if (pollEvents & POLLIN) {
awoken();
} else {
LOGW("Ignoring unexpected poll events 0x%x on wake read pipe.", pollEvents);
}
} else {
int events = 0;
if (pollEvents & POLLIN) events |= ALOOPER_EVENT_INPUT;
if (pollEvents & POLLOUT) events |= ALOOPER_EVENT_OUTPUT;
if (pollEvents & POLLERR) events |= ALOOPER_EVENT_ERROR;
if (pollEvents & POLLHUP) events |= ALOOPER_EVENT_HANGUP;
if (pollEvents & POLLNVAL) events |= ALOOPER_EVENT_INVALID;
pushResponse(events, mRequests.itemAt(i));
}
if (--eventCount == 0) {
break;
}
}
}
Done:
// Set mPolling to false and wake up the wakeAndLock() waiters.
mPolling = false;
if (mWaiters != 0) {
mAwake.broadcast();
}
#endif
#ifdef LOOPER_STATISTICS
nsecs_t pollEndTime = systemTime(SYSTEM_TIME_MONOTONIC);
mSampledPolls += 1;
if (timeoutMillis == 0) {
mSampledZeroPollCount += 1;
mSampledZeroPollLatencySum += pollEndTime - pollStartTime;
} else if (timeoutMillis > 0 && result == ALOOPER_POLL_TIMEOUT) {
mSampledTimeoutPollCount += 1;
mSampledTimeoutPollLatencySum += pollEndTime - pollStartTime
- milliseconds_to_nanoseconds(timeoutMillis);
}
if (mSampledPolls == SAMPLED_POLLS_TO_AGGREGATE) {
LOGD("%p ~ poll latency statistics: %0.3fms zero timeout, %0.3fms non-zero timeout", this,
0.000001f * float(mSampledZeroPollLatencySum) / mSampledZeroPollCount,
0.000001f * float(mSampledTimeoutPollLatencySum) / mSampledTimeoutPollCount);
mSampledPolls = 0;
mSampledZeroPollCount = 0;
mSampledZeroPollLatencySum = 0;
mSampledTimeoutPollCount = 0;
mSampledTimeoutPollLatencySum = 0;
}
#endif
// Invoke pending message callbacks.
mNextMessageUptime = LLONG_MAX;
while (mMessageEnvelopes.size() != 0) {
nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
const MessageEnvelope& messageEnvelope = mMessageEnvelopes.itemAt(0);
if (messageEnvelope.uptime <= now) {
// Remove the envelope from the list.
// We keep a strong reference to the handler until the call to handleMessage
// finishes. Then we drop it so that the handler can be deleted *before*
// we reacquire our lock.
{ // obtain handler
sp<MessageHandler> handler = messageEnvelope.handler;
Message message = messageEnvelope.message;
mMessageEnvelopes.removeAt(0);
mSendingMessage = true;
mLock.unlock();
#if DEBUG_POLL_AND_WAKE || DEBUG_CALLBACKS
LOGD("%p ~ pollOnce - sending message: handler=%p, what=%d",
this, handler.get(), message.what);
#endif
handler->handleMessage(message);
} // release handler
mLock.lock();
mSendingMessage = false;
result = ALOOPER_POLL_CALLBACK;
} else {
// The last message left at the head of the queue determines the next wakeup time.
mNextMessageUptime = messageEnvelope.uptime;
break;
}
}
// Release lock.
mLock.unlock();
// Invoke all response callbacks.
for (size_t i = 0; i < mResponses.size(); i++) {
const Response& response = mResponses.itemAt(i);
ALooper_callbackFunc callback = response.request.callback;
if (callback) {
int fd = response.request.fd;
int events = response.events;
void* data = response.request.data;
#if DEBUG_POLL_AND_WAKE || DEBUG_CALLBACKS
LOGD("%p ~ pollOnce - invoking fd event callback %p: fd=%d, events=0x%x, data=%p",
this, callback, fd, events, data);
#endif
int callbackResult = callback(fd, events, data);
if (callbackResult == 0) {
removeFd(fd);
}
result = ALOOPER_POLL_CALLBACK;
}
}
return result;
}
int Looper::pollAll(int timeoutMillis, int* outFd, int* outEvents, void** outData) {
if (timeoutMillis <= 0) {
int result;
do {
result = pollOnce(timeoutMillis, outFd, outEvents, outData);
} while (result == ALOOPER_POLL_CALLBACK);
return result;
} else {
nsecs_t endTime = systemTime(SYSTEM_TIME_MONOTONIC)
+ milliseconds_to_nanoseconds(timeoutMillis);
for (;;) {
int result = pollOnce(timeoutMillis, outFd, outEvents, outData);
if (result != ALOOPER_POLL_CALLBACK) {
return result;
}
nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
timeoutMillis = toMillisecondTimeoutDelay(now, endTime);
if (timeoutMillis == 0) {
return ALOOPER_POLL_TIMEOUT;
}
}
}
}
void Looper::wake() {
#if DEBUG_POLL_AND_WAKE
LOGD("%p ~ wake", this);
#endif
#ifdef LOOPER_STATISTICS
// FIXME: Possible race with awoken() but this code is for testing only and is rarely enabled.
if (mPendingWakeCount++ == 0) {
mPendingWakeTime = systemTime(SYSTEM_TIME_MONOTONIC);
}
#endif
ssize_t nWrite;
do {
nWrite = write(mWakeWritePipeFd, "W", 1);
} while (nWrite == -1 && errno == EINTR);
if (nWrite != 1) {
if (errno != EAGAIN) {
LOGW("Could not write wake signal, errno=%d", errno);
}
}
}
void Looper::awoken() {
#if DEBUG_POLL_AND_WAKE
LOGD("%p ~ awoken", this);
#endif
#ifdef LOOPER_STATISTICS
if (mPendingWakeCount == 0) {
LOGD("%p ~ awoken: spurious!", this);
} else {
mSampledWakeCycles += 1;
mSampledWakeCountSum += mPendingWakeCount;
mSampledWakeLatencySum += systemTime(SYSTEM_TIME_MONOTONIC) - mPendingWakeTime;
mPendingWakeCount = 0;
mPendingWakeTime = -1;
if (mSampledWakeCycles == SAMPLED_WAKE_CYCLES_TO_AGGREGATE) {
LOGD("%p ~ wake statistics: %0.3fms wake latency, %0.3f wakes per cycle", this,
0.000001f * float(mSampledWakeLatencySum) / mSampledWakeCycles,
float(mSampledWakeCountSum) / mSampledWakeCycles);
mSampledWakeCycles = 0;
mSampledWakeCountSum = 0;
mSampledWakeLatencySum = 0;
}
}
#endif
char buffer[16];
ssize_t nRead;
do {
nRead = read(mWakeReadPipeFd, buffer, sizeof(buffer));
} while ((nRead == -1 && errno == EINTR) || nRead == sizeof(buffer));
}
void Looper::pushResponse(int events, const Request& request) {
Response response;
response.events = events;
response.request = request;
mResponses.push(response);
}
int Looper::addFd(int fd, int ident, int events, ALooper_callbackFunc callback, void* data) {
#if DEBUG_CALLBACKS
LOGD("%p ~ addFd - fd=%d, ident=%d, events=0x%x, callback=%p, data=%p", this, fd, ident,
events, callback, data);
#endif
if (! callback) {
if (! mAllowNonCallbacks) {
LOGE("Invalid attempt to set NULL callback but not allowed for this looper.");
return -1;
}
if (ident < 0) {
LOGE("Invalid attempt to set NULL callback with ident <= 0.");
return -1;
}
}
#ifdef LOOPER_USES_EPOLL
int epollEvents = 0;
if (events & ALOOPER_EVENT_INPUT) epollEvents |= EPOLLIN;
if (events & ALOOPER_EVENT_OUTPUT) epollEvents |= EPOLLOUT;
{ // acquire lock
AutoMutex _l(mLock);
Request request;
request.fd = fd;
request.ident = ident;
request.callback = callback;
request.data = data;
struct epoll_event eventItem;
memset(& eventItem, 0, sizeof(epoll_event)); // zero out unused members of data field union
eventItem.events = epollEvents;
eventItem.data.fd = fd;
ssize_t requestIndex = mRequests.indexOfKey(fd);
if (requestIndex < 0) {
int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, fd, & eventItem);
if (epollResult < 0) {
LOGE("Error adding epoll events for fd %d, errno=%d", fd, errno);
return -1;
}
mRequests.add(fd, request);
} else {
int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_MOD, fd, & eventItem);
if (epollResult < 0) {
LOGE("Error modifying epoll events for fd %d, errno=%d", fd, errno);
return -1;
}
mRequests.replaceValueAt(requestIndex, request);
}
} // release lock
#else
int pollEvents = 0;
if (events & ALOOPER_EVENT_INPUT) pollEvents |= POLLIN;
if (events & ALOOPER_EVENT_OUTPUT) pollEvents |= POLLOUT;
wakeAndLock(); // acquire lock
struct pollfd requestedFd;
requestedFd.fd = fd;
requestedFd.events = pollEvents;
Request request;
request.fd = fd;
request.ident = ident;
request.callback = callback;
request.data = data;
ssize_t index = getRequestIndexLocked(fd);
if (index < 0) {
mRequestedFds.push(requestedFd);
mRequests.push(request);
} else {
mRequestedFds.replaceAt(requestedFd, size_t(index));
mRequests.replaceAt(request, size_t(index));
}
mLock.unlock(); // release lock
#endif
return 1;
}
int Looper::removeFd(int fd) {
#if DEBUG_CALLBACKS
LOGD("%p ~ removeFd - fd=%d", this, fd);
#endif
#ifdef LOOPER_USES_EPOLL
{ // acquire lock
AutoMutex _l(mLock);
ssize_t requestIndex = mRequests.indexOfKey(fd);
if (requestIndex < 0) {
return 0;
}
int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_DEL, fd, NULL);
if (epollResult < 0) {
LOGE("Error removing epoll events for fd %d, errno=%d", fd, errno);
return -1;
}
mRequests.removeItemsAt(requestIndex);
} // release lock
return 1;
#else
wakeAndLock(); // acquire lock
ssize_t index = getRequestIndexLocked(fd);
if (index >= 0) {
mRequestedFds.removeAt(size_t(index));
mRequests.removeAt(size_t(index));
}
mLock.unlock(); // release lock
return index >= 0;
#endif
}
#ifndef LOOPER_USES_EPOLL
ssize_t Looper::getRequestIndexLocked(int fd) {
size_t requestCount = mRequestedFds.size();
for (size_t i = 0; i < requestCount; i++) {
if (mRequestedFds.itemAt(i).fd == fd) {
return i;
}
}
return -1;
}
void Looper::wakeAndLock() {
mLock.lock();
mWaiters += 1;
while (mPolling) {
wake();
mAwake.wait(mLock);
}
mWaiters -= 1;
if (mWaiters == 0) {
mResume.signal();
}
}
#endif
void Looper::sendMessage(const sp<MessageHandler>& handler, const Message& message) {
nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
sendMessageAtTime(now, handler, message);
}
void Looper::sendMessageDelayed(nsecs_t uptimeDelay, const sp<MessageHandler>& handler,
const Message& message) {
nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
sendMessageAtTime(now + uptimeDelay, handler, message);
}
void Looper::sendMessageAtTime(nsecs_t uptime, const sp<MessageHandler>& handler,
const Message& message) {
#if DEBUG_CALLBACKS
LOGD("%p ~ sendMessageAtTime - uptime=%lld, handler=%p, what=%d",
this, uptime, handler.get(), message.what);
#endif
size_t i = 0;
{ // acquire lock
AutoMutex _l(mLock);
size_t messageCount = mMessageEnvelopes.size();
while (i < messageCount && uptime >= mMessageEnvelopes.itemAt(i).uptime) {
i += 1;
}
MessageEnvelope messageEnvelope(uptime, handler, message);
mMessageEnvelopes.insertAt(messageEnvelope, i, 1);
// Optimization: If the Looper is currently sending a message, then we can skip
// the call to wake() because the next thing the Looper will do after processing
// messages is to decide when the next wakeup time should be. In fact, it does
// not even matter whether this code is running on the Looper thread.
if (mSendingMessage) {
return;
}
} // release lock
// Wake the poll loop only when we enqueue a new message at the head.
if (i == 0) {
wake();
}
}
void Looper::removeMessages(const sp<MessageHandler>& handler) {
#if DEBUG_CALLBACKS
LOGD("%p ~ removeMessages - handler=%p", this, handler.get());
#endif
{ // acquire lock
AutoMutex _l(mLock);
for (size_t i = mMessageEnvelopes.size(); i != 0; ) {
const MessageEnvelope& messageEnvelope = mMessageEnvelopes.itemAt(--i);
if (messageEnvelope.handler == handler) {
mMessageEnvelopes.removeAt(i);
}
}
} // release lock
}
void Looper::removeMessages(const sp<MessageHandler>& handler, int what) {
#if DEBUG_CALLBACKS
LOGD("%p ~ removeMessages - handler=%p, what=%d", this, handler.get(), what);
#endif
{ // acquire lock
AutoMutex _l(mLock);
for (size_t i = mMessageEnvelopes.size(); i != 0; ) {
const MessageEnvelope& messageEnvelope = mMessageEnvelopes.itemAt(--i);
if (messageEnvelope.handler == handler
&& messageEnvelope.message.what == what) {
mMessageEnvelopes.removeAt(i);
}
}
} // release lock
}
} // namespace android