/*
- * Copyright 2014 Facebook, Inc.
+ * Copyright 2013-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.
#pragma once
#include <atomic>
+#include <cassert>
#include <chrono>
#include <limits>
-#include <assert.h>
-#include <unistd.h>
+
#include <boost/noncopyable.hpp>
+#include <folly/portability/Unistd.h>
+
namespace folly { namespace detail {
enum class FutexResult {
VALUE_CHANGED, /* Futex value didn't match expected */
AWOKEN, /* futex wait matched with a futex wake */
INTERRUPTED, /* Spurious wake-up or signal caused futex wait failure */
- TIMEDOUT
+ TIMEDOUT,
};
/**
template <template <typename> class Atom = std::atomic>
struct Futex : Atom<uint32_t>, boost::noncopyable {
- explicit Futex(uint32_t init = 0) : Atom<uint32_t>(init) {}
+ explicit constexpr Futex(uint32_t init = 0) : Atom<uint32_t>(init) {}
/** Puts the thread to sleep if this->load() == expected. Returns true when
* it is returning because it has consumed a wake() event, false for any
}
}
- /** Wakens up to count waiters where (waitMask & wakeMask) != 0,
- * returning the number of awoken threads. */
+ /** Wakens up to count waiters where (waitMask & wakeMask) !=
+ * 0, returning the number of awoken threads, or -1 if an error
+ * occurred. Note that when constructing a concurrency primitive
+ * that can guard its own destruction, it is likely that you will
+ * want to ignore EINVAL here (as well as making sure that you
+ * never touch the object after performing the memory store that
+ * is the linearization point for unlock or control handoff).
+ * See https://sourceware.org/bugzilla/show_bug.cgi?id=13690 */
int futexWake(int count = std::numeric_limits<int>::max(),
uint32_t wakeMask = -1);
* is the same as system_clock on some platforms. */
FutexResult futexWaitImpl(
uint32_t expected,
- std::chrono::time_point<std::chrono::system_clock>* absSystemTime,
- std::chrono::time_point<std::chrono::steady_clock>* absSteadyTime,
+ std::chrono::system_clock::time_point const* absSystemTime,
+ std::chrono::steady_clock::time_point const* absSteadyTime,
uint32_t waitMask);
};
EmulatedFutexAtomic() noexcept = default;
constexpr /* implicit */ EmulatedFutexAtomic(T init) noexcept
: std::atomic<T>(init) {}
- EmulatedFutexAtomic(const EmulatedFutexAtomic& rhs) = delete;
+ // It doesn't copy or move
+ EmulatedFutexAtomic(EmulatedFutexAtomic&& rhs) = delete;
};
/* Available specializations, with definitions elsewhere */
-template<>
+template <>
int Futex<std::atomic>::futexWake(int count, uint32_t wakeMask);
-template<>
+template <>
FutexResult Futex<std::atomic>::futexWaitImpl(
- uint32_t expected,
- std::chrono::time_point<std::chrono::system_clock>* absSystemTime,
- std::chrono::time_point<std::chrono::steady_clock>* absSteadyTime,
- uint32_t waitMask);
+ uint32_t expected,
+ std::chrono::system_clock::time_point const* absSystemTime,
+ std::chrono::steady_clock::time_point const* absSteadyTime,
+ uint32_t waitMask);
-template<>
+template <>
int Futex<EmulatedFutexAtomic>::futexWake(int count, uint32_t wakeMask);
-template<>
+template <>
FutexResult Futex<EmulatedFutexAtomic>::futexWaitImpl(
- uint32_t expected,
- std::chrono::time_point<std::chrono::system_clock>* absSystemTime,
- std::chrono::time_point<std::chrono::steady_clock>* absSteadyTime,
- uint32_t waitMask);
+ uint32_t expected,
+ std::chrono::system_clock::time_point const* absSystemTime,
+ std::chrono::steady_clock::time_point const* absSteadyTime,
+ uint32_t waitMask);
-}}
+} // namespace detail
+} // namespace folly