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// Copyright 2023 The Dawn & Tint Authors
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
// list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifndef SRC_DAWN_NATIVE_SYSTEMEVENT_H_
#define SRC_DAWN_NATIVE_SYSTEMEVENT_H_
#include <optional>
#include <utility>
#include "dawn/common/MutexProtected.h"
#include "dawn/common/NonCopyable.h"
#include "dawn/common/Platform.h"
#include "dawn/common/RefCounted.h"
#include "dawn/native/IntegerTypes.h"
#include "dawn/native/SystemHandle.h"
namespace dawn::native {
struct TrackedFutureWaitInfo;
class SystemEventPipeSender;
// SystemEventReceiver holds an OS event primitive (Win32 Event Object or POSIX file descriptor (fd)
// that will be signalled by some other thing: either an OS integration like SetEventOnCompletion(),
// or our own code like SystemEventPipeSender.
//
// SystemEventReceiver is one-time-use (to make it easier to use correctly) - once it's been
// signalled, it won't ever get reset (become unsignalled). Instead, if we want to reuse underlying
// OS objects, it should be reset and recycled *after* the SystemEventReceiver and
// SystemEventPipeSender have been destroyed.
class SystemEventReceiver final : NonCopyable {
public:
static SystemEventReceiver CreateAlreadySignaled();
SystemEventReceiver() = default;
explicit SystemEventReceiver(SystemHandle primitive);
SystemEventReceiver(SystemEventReceiver&&) = default;
SystemEventReceiver& operator=(SystemEventReceiver&&) = default;
private:
template <typename It>
friend bool WaitAnySystemEvent(It begin, It end, Nanoseconds timeout);
friend std::pair<SystemEventPipeSender, SystemEventReceiver> CreateSystemEventPipe();
SystemHandle mPrimitive;
};
// See CreateSystemEventPipe.
class SystemEventPipeSender final : NonCopyable {
public:
SystemEventPipeSender() = default;
SystemEventPipeSender(SystemEventPipeSender&&) = default;
SystemEventPipeSender& operator=(SystemEventPipeSender&&) = default;
~SystemEventPipeSender();
bool IsValid() const;
void Signal() &&;
private:
friend std::pair<SystemEventPipeSender, SystemEventReceiver> CreateSystemEventPipe();
SystemHandle mPrimitive;
};
// CreateSystemEventPipe provides an SystemEventReceiver that can be signalled by Dawn code. This is
// useful for queue completions on Metal (where Metal signals us by calling a callback) and for
// async pipeline creations that happen in a worker-thread task.
//
// We use OS events even for these because, unlike C++/pthreads primitives (mutexes, atomics,
// condvars, etc.), it's possible to wait-any on them (wait for any of a list of events to fire).
// Other use-cases in Dawn that don't require wait-any should generally use C++ primitives, for
// example for signalling the completion of other types of worker-thread work that don't need to
// signal a WGPUFuture.
//
// SystemEventReceiver is one-time-use (see its docs), so there's no way to reset an
// SystemEventPipeSender.
//
// - On Windows, SystemEventReceiver is a Win32 Event Object, so we can create one with
// CreateEvent() and signal it with SetEvent().
// - On POSIX, SystemEventReceiver is a file descriptor (fd), so we can create one with pipe(), and
// signal it by write()ing into the pipe (to make it become readable, though we won't read() it).
std::pair<SystemEventPipeSender, SystemEventReceiver> CreateSystemEventPipe();
class SystemEvent : public RefCounted {
public:
bool IsSignaled() const;
void Signal();
// Lazily create a system event receiver. Immediately after this receiver
// is signaled, IsSignaled should always return true.
const SystemEventReceiver& GetOrCreateSystemEventReceiver();
private:
// mSignaled indicates whether the event has already been signaled.
// It is stored outside the mPipe mutex so its status can quickly be checked without
// acquiring a lock.
std::atomic<bool> mSignaled{false};
MutexProtected<std::optional<std::pair<SystemEventPipeSender, SystemEventReceiver>>> mPipe;
};
} // namespace dawn::native
#endif // SRC_DAWN_NATIVE_SYSTEMEVENT_H_