#pragma once
#include <fcntl.h>
+#include <poll.h>
#include <sys/types.h>
#include <unistd.h>
#ifdef FOLLY_HAVE_EVENTFD
if (fdType == FdType::EVENTFD) {
- eventfd_ = eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK | EFD_SEMAPHORE);
+ eventfd_ = eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK);
if (eventfd_ == -1) {
if (errno == ENOSYS || errno == EINVAL) {
// eventfd not availalble
* unmodified.
*/
bool tryConsume(MessageT& result) {
+ SCOPE_EXIT { syncSignalAndQueue(); };
+
checkPid();
- try {
+ folly::SpinLockGuard g(spinlock_);
- folly::SpinLockGuard g(spinlock_);
+ if (UNLIKELY(queue_.empty())) {
+ return false;
+ }
- if (UNLIKELY(queue_.empty())) {
- return false;
- }
+ auto data = std::move(queue_.front());
+ result = data.first;
+ RequestContext::setContext(data.second);
- auto data = std::move(queue_.front());
- result = data.first;
- RequestContext::setContext(data.second);
-
- queue_.pop_front();
- } catch (...) {
- // Handle an exception if the assignment operator happens to throw.
- // We consumed an event but weren't able to pop the message off the
- // queue. Signal the event again since the message is still in the
- // queue.
- signalEvent(1);
- throw;
- }
+ queue_.pop_front();
return true;
}
mutable std::atomic<int> maxEventBytes_{0};
#endif
- inline void signalEvent(size_t numAdded = 1) const {
- static const uint8_t kPipeMessage[] = {
- 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1
- };
+ void ensureSignalLocked() const {
+ // semantics: empty fd == empty queue <=> !signal_
+ if (signal_) {
+ return;
+ }
ssize_t bytes_written = 0;
ssize_t bytes_expected = 0;
- if (eventfd_ >= 0) {
- // eventfd(2) dictates that we must write a 64-bit integer
- uint64_t numAdded64(numAdded);
- bytes_expected = static_cast<ssize_t>(sizeof(numAdded64));
- bytes_written = ::write(eventfd_, &numAdded64, sizeof(numAdded64));
- } else {
- // pipe semantics, add one message for each numAdded
- bytes_expected = numAdded;
- do {
- size_t messageSize = std::min(numAdded, sizeof(kPipeMessage));
- ssize_t rc = ::write(pipeFds_[1], kPipeMessage, messageSize);
- if (rc < 0) {
- // TODO: if the pipe is full, write will fail with EAGAIN.
- // See task #1044651 for how this could be handled
- break;
- }
- numAdded -= rc;
- bytes_written += rc;
- } while (numAdded > 0);
- }
+
+ do {
+ if (eventfd_ >= 0) {
+ // eventfd(2) dictates that we must write a 64-bit integer
+ uint64_t signal = 1;
+ bytes_expected = static_cast<ssize_t>(sizeof(signal));
+ bytes_written = ::write(eventfd_, &signal, bytes_expected);
+ } else {
+ uint8_t signal = 1;
+ bytes_expected = static_cast<ssize_t>(sizeof(signal));
+ bytes_written = ::write(pipeFds_[1], &signal, bytes_expected);
+ }
+ } while (bytes_written == -1 && errno == EINTR);
+
#ifdef __ANDROID__
- eventBytes_ += bytes_written;
- maxEventBytes_ = std::max((int)maxEventBytes_, (int)eventBytes_);
+ if (bytes_written > 0) {
+ eventBytes_ += bytes_written;
+ maxEventBytes_ = std::max((int)maxEventBytes_, (int)eventBytes_);
+ }
#endif
- if (bytes_written != bytes_expected) {
+ if (bytes_written == bytes_expected) {
+ signal_ = true;
+ } else {
#ifdef __ANDROID__
LOG(ERROR) << "NotificationQueue Write Error=" << errno
<< " bytesInPipe=" << eventBytes_
}
}
- bool tryConsumeEvent() {
- uint64_t value = 0;
- ssize_t rc = -1;
- if (eventfd_ >= 0) {
- rc = readNoInt(eventfd_, &value, sizeof(value));
+ void drainSignalsLocked() {
+ ssize_t bytes_read = 0;
+ if (eventfd_ > 0) {
+ uint64_t message;
+ bytes_read = readNoInt(eventfd_, &message, sizeof(message));
+ CHECK(bytes_read != -1 || errno == EAGAIN);
} else {
- uint8_t value8;
- rc = readNoInt(pipeFds_[0], &value8, sizeof(value8));
- value = value8;
+ // There should only be one byte in the pipe. To avoid potential leaks we still drain.
+ uint8_t message[32];
+ ssize_t result;
+ while ((result = readNoInt(pipeFds_[0], &message, sizeof(message))) != -1) {
+ bytes_read += result;
+ }
+ CHECK(result == -1 && errno == EAGAIN);
+ LOG_IF(ERROR, bytes_read > 1)
+ << "[NotificationQueue] Unexpected state while draining pipe: bytes_read="
+ << bytes_read << " bytes, expected <= 1";
+ }
+ LOG_IF(ERROR, (signal_ && bytes_read == 0) || (!signal_ && bytes_read > 0))
+ << "[NotificationQueue] Unexpected state while draining signals: signal_="
+ << signal_ << " bytes_read=" << bytes_read;
+
+ signal_ = false;
+
#ifdef __ANDROID__
- eventBytes_ -= 1;
-#endif
+ if (bytes_read > 0) {
+ eventBytes_ -= bytes_read;
}
- if (rc < 0) {
- // EAGAIN should pretty much be the only error we can ever get.
- // This means someone else already processed the only available message.
- CHECK_EQ(errno, EAGAIN);
- return false;
+#endif
+ }
+
+ void ensureSignal() const {
+ folly::SpinLockGuard g(spinlock_);
+ ensureSignalLocked();
+ }
+
+ void syncSignalAndQueue() {
+ folly::SpinLockGuard g(spinlock_);
+
+ if (queue_.empty()) {
+ drainSignalsLocked();
+ } else {
+ ensureSignalLocked();
}
- assert(value == 1);
- return true;
}
bool putMessageImpl(MessageT&& message, size_t maxSize, bool throws=true) {
signal = true;
}
queue_.emplace_back(std::move(message), RequestContext::saveContext());
- }
- if (signal) {
- signalEvent();
+ if (signal) {
+ ensureSignalLocked();
+ }
}
return true;
}
signal = true;
}
queue_.emplace_back(message, RequestContext::saveContext());
- }
- if (signal) {
- signalEvent();
+ if (signal) {
+ ensureSignalLocked();
+ }
}
return true;
}
if (numActiveConsumers_ < numConsumers_) {
signal = true;
}
- }
- if (signal) {
- signalEvent();
+ if (signal) {
+ ensureSignalLocked();
+ }
}
}
mutable folly::SpinLock spinlock_;
+ mutable bool signal_{false};
int eventfd_;
int pipeFds_[2]; // to fallback to on older/non-linux systems
uint32_t advisoryMaxQueueSize_;
bool isDrain, size_t* numConsumed) noexcept {
DestructorGuard dg(this);
uint32_t numProcessed = 0;
- bool firstRun = true;
setActive(true);
+ SCOPE_EXIT {
+ if (queue_) {
+ queue_->syncSignalAndQueue();
+ }
+ };
SCOPE_EXIT { setActive(false, /* shouldLock = */ true); };
SCOPE_EXIT {
if (numConsumed != nullptr) {
}
};
while (true) {
- // Try to decrement the eventfd.
- //
- // The eventfd is only used to wake up the consumer - there may or
- // may not actually be an event available (another consumer may
- // have read it). We don't really care, we only care about
- // emptying the queue.
- if (!isDrain && firstRun) {
- queue_->tryConsumeEvent();
- firstRun = false;
- }
-
// Now pop the message off of the queue.
//
// We have to manually acquire and release the spinlock here, rather than
++numProcessed;
if (!isDrain && maxReadAtOnce_ > 0 &&
numProcessed >= maxReadAtOnce_) {
- queue_->signalEvent(1);
return;
}
if (locked) {
// Unlock the spinlock.
queue_->spinlock_.unlock();
-
- // Push a notification back on the eventfd since we didn't actually
- // read the message off of the queue.
- if (!isDrain) {
- queue_->signalEvent(1);
- }
}
return;
folly::SpinLockGuard g(queue_->spinlock_);
queue_->numConsumers_++;
}
- queue_->signalEvent();
+ queue_->ensureSignal();
if (queue_->eventfd_ >= 0) {
initHandler(eventBase, queue_->eventfd_);
projects / folly.git / commitdiff