1 //===- llvm/System/Mutex.h - Mutex Operating System Concept -----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file declares the llvm::sys::Mutex class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_SYSTEM_MUTEX_H
15 #define LLVM_SYSTEM_MUTEX_H
17 #include "llvm/Support/Threading.h"
24 /// @brief Platform agnostic Mutex class.
27 /// @name Constructors
31 /// Initializes the lock but doesn't acquire it. if \p recursive is set
32 /// to false, the lock will not be recursive which makes it cheaper but
33 /// also more likely to deadlock (same thread can't acquire more than
35 /// @brief Default Constructor.
36 explicit MutexImpl(bool recursive = true);
38 /// Releases and removes the lock
47 /// Attempts to unconditionally acquire the lock. If the lock is held by
48 /// another thread, this method will wait until it can acquire the lock.
49 /// @returns false if any kind of error occurs, true otherwise.
50 /// @brief Unconditionally acquire the lock.
53 /// Attempts to release the lock. If the lock is held by the current
54 /// thread, the lock is released allowing other threads to acquire the
56 /// @returns false if any kind of error occurs, true otherwise.
57 /// @brief Unconditionally release the lock.
60 /// Attempts to acquire the lock without blocking. If the lock is not
61 /// available, this function returns false quickly (without blocking). If
62 /// the lock is available, it is acquired.
63 /// @returns false if any kind of error occurs or the lock is not
64 /// available, true otherwise.
65 /// @brief Try to acquire the lock.
69 /// @name Platform Dependent Data
72 void* data_; ///< We don't know what the data will be
75 /// @name Do Not Implement
78 MutexImpl(const MutexImpl & original);
79 void operator=(const MutexImpl &);
84 /// SmartMutex - A mutex with a compile time constant parameter that
85 /// indicates whether this mutex should become a no-op when we're not
86 /// running in multithreaded mode.
87 template<bool mt_only>
88 class SmartMutex : public MutexImpl {
92 explicit SmartMutex(bool rec = true) :
93 MutexImpl(rec), acquired(0), recursive(rec) { }
96 if (!mt_only || llvm_is_multithreaded()) {
97 return MutexImpl::acquire();
99 // Single-threaded debugging code. This would be racy in
100 // multithreaded mode, but provides not sanity checks in single
102 assert((recursive || acquired == 0) && "Lock already acquired!!");
109 if (!mt_only || llvm_is_multithreaded()) {
110 return MutexImpl::release();
112 // Single-threaded debugging code. This would be racy in
113 // multithreaded mode, but provides not sanity checks in single
115 assert(((recursive && acquired) || (acquired == 1)) &&
116 "Lock not acquired before release!");
123 if (!mt_only || llvm_is_multithreaded())
124 return MutexImpl::tryacquire();
129 SmartMutex(const SmartMutex<mt_only> & original);
130 void operator=(const SmartMutex<mt_only> &);
133 /// Mutex - A standard, always enforced mutex.
134 typedef SmartMutex<false> Mutex;
136 template<bool mt_only>
137 class SmartScopedLock {
138 SmartMutex<mt_only>& mtx;
141 SmartScopedLock(SmartMutex<mt_only>& m) : mtx(m) {
150 typedef SmartScopedLock<false> ScopedLock;