lib/System/Mutex.cpp

   1 //===- Mutex.cpp - Mutual Exclusion Lock ------------------------*- C++ -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements the llvm::sys::Mutex class.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Config/config.h"
  15 #include "llvm/System/Mutex.h"
  16
  17 //===----------------------------------------------------------------------===//
  18 //=== WARNING: Implementation here must contain only TRULY operating system
  19 //===          independent code.
  20 //===----------------------------------------------------------------------===//
  21
  22 #if !defined(ENABLE_THREADS) || ENABLE_THREADS == 0
  23 // Define all methods as no-ops if threading is explicitly disabled
  24 namespace llvm {
  25 using namespace sys;
  26 MutexImpl::MutexImpl( bool recursive) { }
  27 MutexImpl::~MutexImpl() { }
  28 bool MutexImpl::acquire() { return true; }
  29 bool MutexImpl::release() { return true; }
  30 bool MutexImpl::tryacquire() { return true; }
  31 }
  32 #else
  33
  34 #if defined(HAVE_PTHREAD_H) && defined(HAVE_PTHREAD_MUTEX_LOCK)
  35
  36 #include <cassert>
  37 #include <pthread.h>
  38 #include <stdlib.h>
  39
  40 namespace llvm {
  41 using namespace sys;
  42
  43
  44 // This variable is useful for situations where the pthread library has been
  45 // compiled with weak linkage for its interface symbols. This allows the
  46 // threading support to be turned off by simply not linking against -lpthread.
  47 // In that situation, the value of pthread_mutex_init will be 0 and
  48 // consequently pthread_enabled will be false. In such situations, all the
  49 // pthread operations become no-ops and the functions all return false. If
  50 // pthread_mutex_init does have an address, then mutex support is enabled.
  51 // Note: all LLVM tools will link against -lpthread if its available since it
  52 //       is configured into the LIBS variable.
  53 // Note: this line of code generates a warning if pthread_mutex_init is not
  54 //       declared with weak linkage. It's safe to ignore the warning.
  55 static const bool pthread_enabled = true;
  56
  57 // Construct a Mutex using pthread calls
  58 MutexImpl::MutexImpl( bool recursive)
  59   : data_(0)
  60 {
  61   if (pthread_enabled)
  62   {
  63     // Declare the pthread_mutex data structures
  64     pthread_mutex_t* mutex =
  65       static_cast<pthread_mutex_t*>(malloc(sizeof(pthread_mutex_t)));
  66     pthread_mutexattr_t attr;
  67
  68     // Initialize the mutex attributes
  69     int errorcode = pthread_mutexattr_init(&attr);
  70     assert(errorcode == 0);
  71
  72     // Initialize the mutex as a recursive mutex, if requested, or normal
  73     // otherwise.
  74     int kind = ( recursive  ? PTHREAD_MUTEX_RECURSIVE : PTHREAD_MUTEX_NORMAL );
  75     errorcode = pthread_mutexattr_settype(&attr, kind);
  76     assert(errorcode == 0);
  77
  78 #if !defined(__FreeBSD__) && !defined(__OpenBSD__) && !defined(__NetBSD__) && !defined(__DragonFly__)
  79     // Make it a process local mutex
  80     errorcode = pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_PRIVATE);
  81 #endif
  82
  83     // Initialize the mutex
  84     errorcode = pthread_mutex_init(mutex, &attr);
  85     assert(errorcode == 0);
  86
  87     // Destroy the attributes
  88     errorcode = pthread_mutexattr_destroy(&attr);
  89     assert(errorcode == 0);
  90
  91     // Assign the data member
  92     data_ = mutex;
  93   }
  94 }
  95
  96 // Destruct a Mutex
  97 MutexImpl::~MutexImpl()
  98 {
  99   if (pthread_enabled)
 100   {
 101     pthread_mutex_t* mutex = static_cast<pthread_mutex_t*>(data_);
 102     assert(mutex != 0);
 103     pthread_mutex_destroy(mutex);
 104     free(mutex);
 105   }
 106 }
 107
 108 bool
 109 MutexImpl::acquire()
 110 {
 111   if (pthread_enabled)
 112   {
 113     pthread_mutex_t* mutex = static_cast<pthread_mutex_t*>(data_);
 114     assert(mutex != 0);
 115
 116     int errorcode = pthread_mutex_lock(mutex);
 117     return errorcode == 0;
 118   } else return false;
 119 }
 120
 121 bool
 122 MutexImpl::release()
 123 {
 124   if (pthread_enabled)
 125   {
 126     pthread_mutex_t* mutex = static_cast<pthread_mutex_t*>(data_);
 127     assert(mutex != 0);
 128
 129     int errorcode = pthread_mutex_unlock(mutex);
 130     return errorcode == 0;
 131   } else return false;
 132 }
 133
 134 bool
 135 MutexImpl::tryacquire()
 136 {
 137   if (pthread_enabled)
 138   {
 139     pthread_mutex_t* mutex = static_cast<pthread_mutex_t*>(data_);
 140     assert(mutex != 0);
 141
 142     int errorcode = pthread_mutex_trylock(mutex);
 143     return errorcode == 0;
 144   } else return false;
 145 }
 146
 147 }
 148
 149 #elif defined(LLVM_ON_UNIX)
 150 #include "Unix/Mutex.inc"
 151 #elif defined( LLVM_ON_WIN32)
 152 #include "Win32/Mutex.inc"
 153 #else
 154 #warning Neither LLVM_ON_UNIX nor LLVM_ON_WIN32 was set in System/Mutex.cpp
 155 #endif
 156 #endif
 157