/*
- * Copyright 2016 Facebook, Inc.
+ * Copyright 2012-present Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* limitations under the License.
*/
-#ifndef FOLLY_EXPERIMENTAL_EVENTCOUNT_H_
-#define FOLLY_EXPERIMENTAL_EVENTCOUNT_H_
+#pragma once
-#include <unistd.h>
-#include <syscall.h>
-#include <linux/futex.h>
-#include <sys/time.h>
-#include <climits>
#include <atomic>
+#include <climits>
#include <thread>
+
#include <glog/logging.h>
-#include <folly/Bits.h>
#include <folly/Likely.h>
-
+#include <folly/detail/Futex.h>
+#include <folly/lang/Bits.h>
+#include <folly/portability/SysTime.h>
+#include <folly/portability/Unistd.h>
namespace folly {
-namespace detail {
-
-inline int futex(int* uaddr, int op, int val, const timespec* timeout,
- int* uaddr2, int val3) noexcept {
- return syscall(SYS_futex, uaddr, op, val, timeout, uaddr2, val3);
-}
-
-} // namespace detail
-
/**
* Event count: a condition variable for lock free algorithms.
*
static_assert(sizeof(int) == 4, "bad platform");
static_assert(sizeof(uint32_t) == 4, "bad platform");
static_assert(sizeof(uint64_t) == 8, "bad platform");
+ static_assert(sizeof(std::atomic<uint64_t>) == 8, "bad platform");
+ static_assert(sizeof(detail::Futex<std::atomic>) == 4, "bad platform");
-#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
- static constexpr size_t kEpochOffset = 1;
-#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
- static constexpr size_t kEpochOffset = 0; // in units of sizeof(int)
-#else
-# error Your machine uses a weird endianness!
-#endif
+ static constexpr size_t kEpochOffset = kIsLittleEndian ? 1 : 0;
// val_ stores the epoch in the most significant 32 bits and the
// waiter count in the least significant 32 bits.
inline void EventCount::doNotify(int n) noexcept {
uint64_t prev = val_.fetch_add(kAddEpoch, std::memory_order_acq_rel);
if (UNLIKELY(prev & kWaiterMask)) {
- detail::futex(reinterpret_cast<int*>(&val_) + kEpochOffset,
- FUTEX_WAKE, n, nullptr, nullptr, 0);
+ (reinterpret_cast<detail::Futex<std::atomic>*>(&val_) + kEpochOffset)
+ ->futexWake(n);
}
}
inline void EventCount::wait(Key key) noexcept {
while ((val_.load(std::memory_order_acquire) >> kEpochShift) == key.epoch_) {
- detail::futex(reinterpret_cast<int*>(&val_) + kEpochOffset,
- FUTEX_WAIT, key.epoch_, nullptr, nullptr, 0);
+ (reinterpret_cast<detail::Futex<std::atomic>*>(&val_) + kEpochOffset)
+ ->futexWait(key.epoch_);
}
// memory_order_relaxed would suffice for correctness, but the faster
// #waiters gets to 0, the less likely it is that we'll do spurious wakeups
template <class Condition>
void EventCount::await(Condition condition) {
- if (condition()) return; // fast path
+ if (condition()) {
+ return; // fast path
+ }
// condition() is the only thing that may throw, everything else is
// noexcept, so we can hoist the try/catch block outside of the loop
}
}
-} // namespace folly
-
-#endif /* FOLLY_EXPERIMENTAL_EVENTCOUNT_H_ */
+} // namespace folly