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-rw-r--r--libutils/Looper.cpp87
1 files changed, 71 insertions, 16 deletions
diff --git a/libutils/Looper.cpp b/libutils/Looper.cpp
index 9a2dd6c..ac81090 100644
--- a/libutils/Looper.cpp
+++ b/libutils/Looper.cpp
@@ -20,6 +20,7 @@
#include <unistd.h>
#include <fcntl.h>
#include <limits.h>
+#include <inttypes.h>
namespace android {
@@ -68,7 +69,7 @@ static pthread_key_t gTLSKey = 0;
Looper::Looper(bool allowNonCallbacks) :
mAllowNonCallbacks(allowNonCallbacks), mSendingMessage(false),
- mResponseIndex(0), mNextMessageUptime(LLONG_MAX) {
+ mNextRequestSeq(0), 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);
@@ -84,7 +85,7 @@ Looper::Looper(bool allowNonCallbacks) :
LOG_ALWAYS_FATAL_IF(result != 0, "Could not make wake write pipe non-blocking. errno=%d",
errno);
- mIdling = false;
+ mPolling = false;
// Allocate the epoll instance and register the wake pipe.
mEpollFd = epoll_create(EPOLL_SIZE_HINT);
@@ -206,7 +207,7 @@ int Looper::pollInner(int timeoutMillis) {
timeoutMillis = messageTimeoutMillis;
}
#if DEBUG_POLL_AND_WAKE
- ALOGD("%p ~ pollOnce - next message in %lldns, adjusted timeout: timeoutMillis=%d",
+ ALOGD("%p ~ pollOnce - next message in %" PRId64 "ns, adjusted timeout: timeoutMillis=%d",
this, mNextMessageUptime - now, timeoutMillis);
#endif
}
@@ -217,13 +218,13 @@ int Looper::pollInner(int timeoutMillis) {
mResponseIndex = 0;
// We are about to idle.
- mIdling = true;
+ mPolling = true;
struct epoll_event eventItems[EPOLL_MAX_EVENTS];
int eventCount = epoll_wait(mEpollFd, eventItems, EPOLL_MAX_EVENTS, timeoutMillis);
// No longer idling.
- mIdling = false;
+ mPolling = false;
// Acquire lock.
mLock.lock();
@@ -326,10 +327,14 @@ Done: ;
ALOGD("%p ~ pollOnce - invoking fd event callback %p: fd=%d, events=0x%x, data=%p",
this, response.request.callback.get(), fd, events, data);
#endif
+ // Invoke the callback. Note that the file descriptor may be closed by
+ // the callback (and potentially even reused) before the function returns so
+ // we need to be a little careful when removing the file descriptor afterwards.
int callbackResult = response.request.callback->handleEvent(fd, events, data);
if (callbackResult == 0) {
- removeFd(fd);
+ removeFd(fd, response.request.seq);
}
+
// Clear the callback reference in the response structure promptly because we
// will not clear the response vector itself until the next poll.
response.request.callback.clear();
@@ -437,6 +442,8 @@ int Looper::addFd(int fd, int ident, int events, const sp<LooperCallback>& callb
request.ident = ident;
request.callback = callback;
request.data = data;
+ request.seq = mNextRequestSeq++;
+ if (mNextRequestSeq == -1) mNextRequestSeq = 0; // reserve sequence number -1
struct epoll_event eventItem;
memset(& eventItem, 0, sizeof(epoll_event)); // zero out unused members of data field union
@@ -454,8 +461,29 @@ int Looper::addFd(int fd, int ident, int events, const sp<LooperCallback>& callb
} else {
int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_MOD, fd, & eventItem);
if (epollResult < 0) {
- ALOGE("Error modifying epoll events for fd %d, errno=%d", fd, errno);
- return -1;
+ if (errno == ENOENT) {
+ // Ignore ENOENT because it means that the file descriptor was
+ // closed before its callback was unregistered and meanwhile a new
+ // file descriptor with the same number has been created and is now
+ // being registered for the first time. We tolerate the error since
+ // it may occur naturally when a callback has the side-effect of
+ // closing the file descriptor before returning and unregistering itself.
+ // Callback sequence number checks further ensure that the race is benign.
+#if DEBUG_CALLBACKS
+ ALOGD("%p ~ addFd - EPOLL_CTL_MOD failed due to file descriptor "
+ "being recycled, falling back on EPOLL_CTL_ADD, errno=%d",
+ this, errno);
+#endif
+ epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, fd, & eventItem);
+ if (epollResult < 0) {
+ ALOGE("Error modifying or adding epoll events for fd %d, errno=%d",
+ fd, errno);
+ return -1;
+ }
+ } else {
+ ALOGE("Error modifying epoll events for fd %d, errno=%d", fd, errno);
+ return -1;
+ }
}
mRequests.replaceValueAt(requestIndex, request);
}
@@ -464,8 +492,12 @@ int Looper::addFd(int fd, int ident, int events, const sp<LooperCallback>& callb
}
int Looper::removeFd(int fd) {
+ return removeFd(fd, -1);
+}
+
+int Looper::removeFd(int fd, int seq) {
#if DEBUG_CALLBACKS
- ALOGD("%p ~ removeFd - fd=%d", this, fd);
+ ALOGD("%p ~ removeFd - fd=%d, seq=%d", this, fd, seq);
#endif
{ // acquire lock
@@ -475,13 +507,36 @@ int Looper::removeFd(int fd) {
return 0;
}
- int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_DEL, fd, NULL);
- if (epollResult < 0) {
- ALOGE("Error removing epoll events for fd %d, errno=%d", fd, errno);
- return -1;
+ // Check the sequence number if one was given.
+ if (seq != -1 && mRequests.valueAt(requestIndex).seq != seq) {
+#if DEBUG_CALLBACKS
+ ALOGD("%p ~ removeFd - sequence number mismatch, oldSeq=%d",
+ this, mRequests.valueAt(requestIndex).seq);
+#endif
+ return 0;
}
+ // Always remove the FD from the request map even if an error occurs while
+ // updating the epoll set so that we avoid accidentally leaking callbacks.
mRequests.removeItemsAt(requestIndex);
+
+ int epollResult = epoll_ctl(mEpollFd, EPOLL_CTL_DEL, fd, NULL);
+ if (epollResult < 0) {
+ if (seq != -1 && (errno == EBADF || errno == ENOENT)) {
+ // Ignore EBADF or ENOENT when the sequence number is known because it
+ // means that the file descriptor was closed before its callback was
+ // unregistered. We tolerate the error since it may occur naturally when
+ // a callback has the side-effect of closing the file descriptor before
+ // returning and unregistering itself.
+#if DEBUG_CALLBACKS
+ ALOGD("%p ~ removeFd - EPOLL_CTL_DEL failed due to file descriptor "
+ "being closed, ignoring error, errno=%d", this, errno);
+#endif
+ } else {
+ ALOGE("Error removing epoll events for fd %d, errno=%d", fd, errno);
+ return -1;
+ }
+ }
} // release lock
return 1;
}
@@ -500,7 +555,7 @@ void Looper::sendMessageDelayed(nsecs_t uptimeDelay, const sp<MessageHandler>& h
void Looper::sendMessageAtTime(nsecs_t uptime, const sp<MessageHandler>& handler,
const Message& message) {
#if DEBUG_CALLBACKS
- ALOGD("%p ~ sendMessageAtTime - uptime=%lld, handler=%p, what=%d",
+ ALOGD("%p ~ sendMessageAtTime - uptime=%" PRId64 ", handler=%p, what=%d",
this, uptime, handler.get(), message.what);
#endif
@@ -566,8 +621,8 @@ void Looper::removeMessages(const sp<MessageHandler>& handler, int what) {
} // release lock
}
-bool Looper::isIdling() const {
- return mIdling;
+bool Looper::isPolling() const {
+ return mPolling;
}
} // namespace android
generated by cgit v1.1 at 2025-07-03 15:44:39 +0000