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Commit f4f8284f authored by Jeff Brown's avatar Jeff Brown Committed by Android Git Automerger
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am d577cfd7: Merge "Switch Looper back to using poll() instead of epoll()." into gingerbread 

Merge commit 'd577cfd73a223279f9a5af698f55edd38a3fe4db' into gingerbread-plus-aosp

* commit 'd577cfd73a223279f9a5af698f55edd38a3fe4db':
  Switch Looper back to using poll() instead of epoll().
parents a34207b4 95cefd9b

include/utils/Looper.h

+59 −3
Original line number Diff line number Diff line
@@ -20,9 +20,22 @@ 
#include <utils/threads.h>

#include <utils/RefBase.h>

#include <utils/KeyedVector.h>

#include <utils/Timers.h>



#include <android/looper.h>



// Currently using poll() instead of epoll_wait() since it does a better job of meeting a

// timeout deadline.  epoll_wait() typically causes additional delays of up to 10ms

// beyond the requested timeout.

//#define LOOPER_USES_EPOLL

//#define LOOPER_STATISTICS



#ifdef LOOPER_USES_EPOLL

#include <sys/epoll.h>

#else

#include <sys/poll.h>

#endif



/*

 * Declare a concrete type for the NDK's looper forward declaration.

 */
@@ -190,13 +203,54 @@ private: 


    const bool mAllowNonCallbacks; // immutable



    int mEpollFd; // immutable

    int mWakeReadPipeFd;  // immutable

    int mWakeWritePipeFd; // immutable

    Mutex mLock;



#ifdef LOOPER_USES_EPOLL

    int mEpollFd; // immutable



    // Locked list of file descriptor monitoring requests.

    Mutex mLock;

    KeyedVector<int, Request> mRequests;

    KeyedVector<int, Request> mRequests;  // guarded by mLock

#else

    // The lock guards state used to track whether there is a poll() in progress and whether

    // there are any other threads waiting in wakeAndLock().  The condition variables

    // are used to transfer control among these threads such that all waiters are

    // serviced before a new poll can begin.

    // The wakeAndLock() method increments mWaiters, wakes the poll, blocks on mAwake

    // until mPolling becomes false, then decrements mWaiters again.

    // The poll() method blocks on mResume until mWaiters becomes 0, then sets

    // mPolling to true, blocks until the poll completes, then resets mPolling to false

    // and signals mResume if there are waiters.

    bool mPolling;      // guarded by mLock

    uint32_t mWaiters;  // guarded by mLock

    Condition mAwake;   // guarded by mLock

    Condition mResume;  // guarded by mLock



    Vector<struct pollfd> mRequestedFds;  // must hold mLock and mPolling must be false to modify

    Vector<Request> mRequests;            // must hold mLock and mPolling must be false to modify



    ssize_t getRequestIndexLocked(int fd);

    void wakeAndLock();

#endif



#ifdef LOOPER_STATISTICS

    static const int SAMPLED_WAKE_CYCLES_TO_AGGREGATE = 100;

    static const int SAMPLED_POLLS_TO_AGGREGATE = 1000;



    nsecs_t mPendingWakeTime;

    int mPendingWakeCount;



    int mSampledWakeCycles;

    int mSampledWakeCountSum;

    nsecs_t mSampledWakeLatencySum;



    int mSampledPolls;

    int mSampledZeroPollCount;

    int mSampledZeroPollLatencySum;

    int mSampledTimeoutPollCount;

    int mSampledTimeoutPollLatencySum;

#endif



    // This state is only used privately by pollOnce and does not require a lock since

    // it runs on a single thread.
@@ -204,6 +258,8 @@ private: 
    size_t mResponseIndex;



    int pollInner(int timeoutMillis);

    void awoken();

    void pushResponse(int events, const Request& request);



    static void initTLSKey();

    static void threadDestructor(void *st);

libs/utils/Looper.cpp

+254 −37
Original line number Diff line number Diff line
@@ -19,16 +19,17 @@ 


#include <unistd.h>

#include <fcntl.h>

#include <sys/epoll.h>





namespace android {



#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;
@@ -36,9 +37,6 @@ static pthread_key_t gTLSKey = 0; 
Looper::Looper(bool allowNonCallbacks) :

        mAllowNonCallbacks(allowNonCallbacks),

        mResponseIndex(0) {

    mEpollFd = epoll_create(EPOLL_SIZE_HINT);

    LOG_ALWAYS_FATAL_IF(mEpollFd < 0, "Could not create epoll instance.  errno=%d", errno);



    int wakeFds[2];

    int result = pipe(wakeFds);

    LOG_ALWAYS_FATAL_IF(result != 0, "Could not create wake pipe.  errno=%d", errno);
@@ -54,6 +52,11 @@ Looper::Looper(bool allowNonCallbacks) : 
    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;
@@ -61,12 +64,45 @@ Looper::Looper(bool allowNonCallbacks) : 
    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() {
@@ -157,45 +193,61 @@ int Looper::pollInner(int timeoutMillis) { 
#if DEBUG_POLL_AND_WAKE

    LOGD("%p ~ pollOnce - waiting: timeoutMillis=%d", this, timeoutMillis);

#endif



    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);

    bool acquiredLock = false;

#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



    if (eventCount < 0) {

        if (errno == EINTR) {

            return ALOOPER_POLL_WAKE;

            goto Done;

        }



        LOGW("Poll failed with an unexpected error, errno=%d", errno);

        return ALOOPER_POLL_ERROR;

        result = ALOOPER_POLL_ERROR;

        goto Done;

    }



    if (eventCount == 0) {

#if DEBUG_POLL_AND_WAKE

        LOGD("%p ~ pollOnce - timeout", this);

#endif

        return ALOOPER_POLL_TIMEOUT;

        result = ALOOPER_POLL_TIMEOUT;

        goto Done;

    }



    int result = ALOOPER_POLL_WAKE;

    mResponses.clear();

    mResponseIndex = 0;



#if DEBUG_POLL_AND_WAKE

    LOGD("%p ~ pollOnce - handling events from %d fds", this, eventCount);

#endif

    bool acquiredLock = false;



#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) {

#if DEBUG_POLL_AND_WAKE

                LOGD("%p ~ pollOnce - awoken", this);

#endif

                char buffer[16];

                ssize_t nRead;

                do {

                    nRead = read(mWakeReadPipeFd, buffer, sizeof(buffer));

                } while ((nRead == -1 && errno == EINTR) || nRead == sizeof(buffer));

                awoken();

            } else {

                LOGW("Ignoring unexpected epoll events 0x%x on wake read pipe.", epollEvents);

            }
@@ -212,11 +264,7 @@ int Looper::pollInner(int timeoutMillis) { 
                if (epollEvents & EPOLLOUT) events |= ALOOPER_EVENT_OUTPUT;

                if (epollEvents & EPOLLERR) events |= ALOOPER_EVENT_ERROR;

                if (epollEvents & EPOLLHUP) events |= ALOOPER_EVENT_HANGUP;



                Response response;

                response.events = events;

                response.request = mRequests.valueAt(requestIndex);

                mResponses.push(response);

                pushResponse(events, mRequests.valueAt(requestIndex));

            } else {

                LOGW("Ignoring unexpected epoll events 0x%x on fd %d that is "

                        "no longer registered.", epollEvents, fd);
@@ -226,6 +274,66 @@ int Looper::pollInner(int timeoutMillis) { 
    if (acquiredLock) {

        mLock.unlock();

    }

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.

    mLock.lock();

    mPolling = false;

    if (mWaiters != 0) {

        mAwake.broadcast();

    }

    mLock.unlock();

#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



    for (size_t i = 0; i < mResponses.size(); i++) {

        const Response& response = mResponses.itemAt(i);
@@ -278,6 +386,13 @@ void Looper::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);
@@ -290,23 +405,51 @@ void Looper::wake() { 
    }

}



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



    int epollEvents = 0;

    if (events & ALOOPER_EVENT_INPUT) epollEvents |= EPOLLIN;

    if (events & ALOOPER_EVENT_OUTPUT) epollEvents |= EPOLLOUT;

    if (events & ALOOPER_EVENT_ERROR) epollEvents |= EPOLLERR;

    if (events & ALOOPER_EVENT_HANGUP) epollEvents |= EPOLLHUP;



    if (epollEvents == 0) {

        LOGE("Invalid attempt to set a callback with no selected poll events.");

        return -1;

    }



    if (! callback) {

        if (! mAllowNonCallbacks) {

            LOGE("Invalid attempt to set NULL callback but not allowed for this looper.");
@@ -319,6 +462,11 @@ int Looper::addFd(int fd, int ident, int events, ALooper_callbackFunc callback, 
        }

    }



#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);
@@ -350,6 +498,33 @@ int Looper::addFd(int fd, int ident, int events, ALooper_callbackFunc callback, 
            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;

}
@@ -358,6 +533,7 @@ int Looper::removeFd(int fd) { 
    LOGD("%p ~ removeFd - fd=%d", this, fd);

#endif



#ifdef LOOPER_USES_EPOLL

    { // acquire lock

        AutoMutex _l(mLock);

        ssize_t requestIndex = mRequests.indexOfKey(fd);
@@ -372,8 +548,49 @@ int Looper::removeFd(int fd) { 
        }



        mRequests.removeItemsAt(requestIndex);

    } // request lock

    } // 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



} // namespace android

libs/utils/tests/Looper_test.cpp

+0 −8
Original line number Diff line number Diff line
@@ -354,14 +354,6 @@ TEST_F(LooperTest, AddFd_WhenCallbackAdded_ReturnsOne) { 
            << "addFd should return 1 because FD was added";

}



TEST_F(LooperTest, AddFd_WhenEventsIsZero_ReturnsError) {

    Pipe pipe;

    int result = mLooper->addFd(pipe.receiveFd, 0, 0, NULL, NULL);



    EXPECT_EQ(-1, result)

            << "addFd should return -1 because arguments were invalid";

}



TEST_F(LooperTest, AddFd_WhenIdentIsNegativeAndCallbackIsNull_ReturnsError) {

    Pipe pipe;

    int result = mLooper->addFd(pipe.receiveFd, -1, ALOOPER_EVENT_INPUT, NULL, NULL);