e969544232
Unnamed POSIX semaphores are not supported on macOS, nor is timed wait supported on named POSIX semaphores. SysV semaphores have similar limitations. Mach semaphores are one of the only clean ways to create unnamed, shareable semaphores on macOS. As of bug 1734735, we now can transparently send the mach ports across to other processes without much added code, overall making this implementation of Mach semaphores fairly easy. Differential Revision: https://phabricator.services.mozilla.com/D188429
120 lines
3.2 KiB
C++
120 lines
3.2 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_CrossProcessSemaphore_h
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#define mozilla_CrossProcessSemaphore_h
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#include "base/process.h"
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#include "mozilla/TimeStamp.h"
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#include "mozilla/Maybe.h"
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#if defined(XP_WIN) || defined(XP_DARWIN)
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# include "mozilla/UniquePtrExtensions.h"
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#else
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# include <pthread.h>
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# include <semaphore.h>
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# include "mozilla/ipc/SharedMemoryBasic.h"
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# include "mozilla/Atomics.h"
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#endif
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namespace IPC {
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template <typename T>
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struct ParamTraits;
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} // namespace IPC
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//
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// Provides:
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//
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// - CrossProcessSemaphore, a semaphore that can be shared across processes
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namespace mozilla {
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template <typename T>
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inline bool IsHandleValid(const T& handle) {
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return bool(handle);
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}
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#if defined(XP_WIN)
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typedef mozilla::UniqueFileHandle CrossProcessSemaphoreHandle;
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#elif defined(XP_DARWIN)
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typedef mozilla::UniqueMachSendRight CrossProcessSemaphoreHandle;
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#else
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typedef mozilla::ipc::SharedMemoryBasic::Handle CrossProcessSemaphoreHandle;
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template <>
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inline bool IsHandleValid<CrossProcessSemaphoreHandle>(
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const CrossProcessSemaphoreHandle& handle) {
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return !(handle == mozilla::ipc::SharedMemoryBasic::NULLHandle());
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}
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#endif
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class CrossProcessSemaphore {
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public:
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/**
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* CrossProcessSemaphore
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* @param name A name which can reference this lock (currently unused)
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**/
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static CrossProcessSemaphore* Create(const char* aName,
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uint32_t aInitialValue);
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/**
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* CrossProcessSemaphore
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* @param handle A handle of an existing cross process semaphore that can be
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* opened.
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*/
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static CrossProcessSemaphore* Create(CrossProcessSemaphoreHandle aHandle);
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~CrossProcessSemaphore();
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/**
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* Decrements the current value of the semaphore. This will block if the
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* current value of the semaphore is 0, up to a maximum of aWaitTime (if
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* specified).
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* Returns true if the semaphore was succesfully decremented, false otherwise.
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**/
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bool Wait(const Maybe<TimeDuration>& aWaitTime = Nothing());
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/**
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* Increments the current value of the semaphore.
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**/
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void Signal();
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/**
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* CloneHandle
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* This function is called to generate a serializable structure that can
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* be sent to the specified process and opened on the other side.
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*
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* @returns A handle that can be shared to another process
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*/
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CrossProcessSemaphoreHandle CloneHandle();
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void CloseHandle();
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private:
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friend struct IPC::ParamTraits<CrossProcessSemaphore>;
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CrossProcessSemaphore();
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CrossProcessSemaphore(const CrossProcessSemaphore&);
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CrossProcessSemaphore& operator=(const CrossProcessSemaphore&);
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#if defined(XP_WIN)
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explicit CrossProcessSemaphore(HANDLE aSemaphore);
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HANDLE mSemaphore;
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#elif defined(XP_DARWIN)
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explicit CrossProcessSemaphore(CrossProcessSemaphoreHandle aSemaphore);
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CrossProcessSemaphoreHandle mSemaphore;
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#else
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RefPtr<mozilla::ipc::SharedMemoryBasic> mSharedBuffer;
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sem_t* mSemaphore;
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mozilla::Atomic<int32_t>* mRefCount;
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#endif
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};
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} // namespace mozilla
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#endif
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