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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164006 91177308-0d34-0410-b5e6-96231b3b80d8
156 lines
4.5 KiB
C++
156 lines
4.5 KiB
C++
//===- llvm/Support/Mutex.h - Mutex Operating System Concept -----*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file declares the llvm::sys::Mutex class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SYSTEM_MUTEX_H
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#define LLVM_SYSTEM_MUTEX_H
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/Threading.h"
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#include <cassert>
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namespace llvm
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{
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namespace sys
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{
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/// @brief Platform agnostic Mutex class.
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class MutexImpl
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{
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/// @name Constructors
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/// @{
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public:
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/// Initializes the lock but doesn't acquire it. if \p recursive is set
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/// to false, the lock will not be recursive which makes it cheaper but
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/// also more likely to deadlock (same thread can't acquire more than
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/// once).
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/// @brief Default Constructor.
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explicit MutexImpl(bool recursive = true);
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/// Releases and removes the lock
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/// @brief Destructor
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~MutexImpl();
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/// @}
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/// @name Methods
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/// @{
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public:
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/// Attempts to unconditionally acquire the lock. If the lock is held by
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/// another thread, this method will wait until it can acquire the lock.
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/// @returns false if any kind of error occurs, true otherwise.
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/// @brief Unconditionally acquire the lock.
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bool acquire();
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/// Attempts to release the lock. If the lock is held by the current
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/// thread, the lock is released allowing other threads to acquire the
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/// lock.
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/// @returns false if any kind of error occurs, true otherwise.
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/// @brief Unconditionally release the lock.
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bool release();
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/// Attempts to acquire the lock without blocking. If the lock is not
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/// available, this function returns false quickly (without blocking). If
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/// the lock is available, it is acquired.
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/// @returns false if any kind of error occurs or the lock is not
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/// available, true otherwise.
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/// @brief Try to acquire the lock.
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bool tryacquire();
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//@}
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/// @name Platform Dependent Data
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/// @{
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private:
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void* data_; ///< We don't know what the data will be
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/// @}
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/// @name Do Not Implement
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/// @{
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private:
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MutexImpl(const MutexImpl &) LLVM_DELETED_FUNCTION;
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void operator=(const MutexImpl &) LLVM_DELETED_FUNCTION;
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/// @}
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};
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/// SmartMutex - A mutex with a compile time constant parameter that
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/// indicates whether this mutex should become a no-op when we're not
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/// running in multithreaded mode.
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template<bool mt_only>
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class SmartMutex : public MutexImpl {
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unsigned acquired;
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bool recursive;
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public:
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explicit SmartMutex(bool rec = true) :
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MutexImpl(rec), acquired(0), recursive(rec) { }
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bool acquire() {
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if (!mt_only || llvm_is_multithreaded()) {
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return MutexImpl::acquire();
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} else {
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// Single-threaded debugging code. This would be racy in
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// multithreaded mode, but provides not sanity checks in single
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// threaded mode.
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assert((recursive || acquired == 0) && "Lock already acquired!!");
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++acquired;
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return true;
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}
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}
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bool release() {
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if (!mt_only || llvm_is_multithreaded()) {
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return MutexImpl::release();
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} else {
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// Single-threaded debugging code. This would be racy in
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// multithreaded mode, but provides not sanity checks in single
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// threaded mode.
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assert(((recursive && acquired) || (acquired == 1)) &&
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"Lock not acquired before release!");
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--acquired;
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return true;
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}
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}
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bool tryacquire() {
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if (!mt_only || llvm_is_multithreaded())
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return MutexImpl::tryacquire();
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else return true;
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}
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private:
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SmartMutex(const SmartMutex<mt_only> & original);
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void operator=(const SmartMutex<mt_only> &);
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};
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/// Mutex - A standard, always enforced mutex.
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typedef SmartMutex<false> Mutex;
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template<bool mt_only>
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class SmartScopedLock {
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SmartMutex<mt_only>& mtx;
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public:
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SmartScopedLock(SmartMutex<mt_only>& m) : mtx(m) {
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mtx.acquire();
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}
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~SmartScopedLock() {
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mtx.release();
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}
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};
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typedef SmartScopedLock<false> ScopedLock;
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}
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}
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#endif
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