lib/System/Mutex.cpp

   1 //===- Mutex.cpp - Mutual Exclusion Lock ------------------------*- C++ -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file was developed by Reid Spencer and is distributed under the
   6 // University of Illinois Open Source 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 #include "llvm/System/IncludeFile.h"
  17
  18 //===----------------------------------------------------------------------===//
  19 //=== WARNING: Implementation here must contain only TRULY operating system
  20 //===          independent code.
  21 //===----------------------------------------------------------------------===//
  22
  23 #if !defined(ENABLE_THREADS) || ENABLE_THREADS == 0
  24 // Define all methods as no-ops if threading is explicitly disabled
  25 namespace llvm {
  26 using namespace sys;
  27 Mutex::Mutex( bool recursive) { }
  28 Mutex::~Mutex() { }
  29 bool Mutex::acquire() { return true; }
  30 bool Mutex::release() { return true; }
  31 bool Mutex::tryacquire() { return true; }
  32 }
  33 #else
  34
  35 #if defined(HAVE_PTHREAD_H) && defined(HAVE_PTHREAD_MUTEX_LOCK)
  36
  37 #include <cassert>
  38 #include <pthread.h>
  39 #include <stdlib.h>
  40
  41 namespace llvm {
  42 using namespace sys;
  43
  44
  45 // This variable is useful for situations where the pthread library has been
  46 // compiled with weak linkage for its interface symbols. This allows the
  47 // threading support to be turned off by simply not linking against -lpthread.
  48 // In that situation, the value of pthread_mutex_init will be 0 and
  49 // consequently pthread_enabled will be false. In such situations, all the
  50 // pthread operations become no-ops and the functions all return false. If
  51 // pthread_mutex_init does have an address, then mutex support is enabled.
  52 // Note: all LLVM tools will link against -lpthread if its available since it
  53 //       is configured into the LIBS variable.
  54 // Note: this line of code generates a warning if pthread_mutex_init is not
  55 //       declared with weak linkage. It's safe to ignore the warning.
  56 static const bool pthread_enabled = true;
  57
  58 // Construct a Mutex using pthread calls
  59 Mutex::Mutex( bool recursive)
  60   : data_(0)
  61 {
  62   if (pthread_enabled)
  63   {
  64     // Declare the pthread_mutex data structures
  65     pthread_mutex_t* mutex =
  66       static_cast<pthread_mutex_t*>(malloc(sizeof(pthread_mutex_t)));
  67     pthread_mutexattr_t attr;
  68
  69     // Initialize the mutex attributes
  70     int errorcode = pthread_mutexattr_init(&attr);
  71     assert(errorcode == 0);
  72
  73     // Initialize the mutex as a recursive mutex, if requested, or normal
  74     // otherwise.
  75     int kind = ( recursive  ? PTHREAD_MUTEX_RECURSIVE : PTHREAD_MUTEX_NORMAL );
  76     errorcode = pthread_mutexattr_settype(&attr, kind);
  77     assert(errorcode == 0);
  78
  79 #if !defined(__FreeBSD__) && !defined(__OpenBSD__) && !defined(__NetBSD__)
  80     // Make it a process local mutex
  81     errorcode = pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_PRIVATE);
  82 #endif
  83
  84     // Initialize the mutex
  85     errorcode = pthread_mutex_init(mutex, &attr);
  86     assert(errorcode == 0);
  87
  88     // Destroy the attributes
  89     errorcode = pthread_mutexattr_destroy(&attr);
  90     assert(errorcode == 0);
  91
  92     // Assign the data member
  93     data_ = mutex;
  94   }
  95 }
  96
  97 // Destruct a Mutex
  98 Mutex::~Mutex()
  99 {
 100   if (pthread_enabled)
 101   {
 102     pthread_mutex_t* mutex = reinterpret_cast<pthread_mutex_t*>(data_);
 103     assert(mutex != 0);
 104     pthread_mutex_destroy(mutex);
 105     assert(mutex != 0);
 106   }
 107 }
 108
 109 bool
 110 Mutex::acquire()
 111 {
 112   if (pthread_enabled)
 113   {
 114     pthread_mutex_t* mutex = reinterpret_cast<pthread_mutex_t*>(data_);
 115     assert(mutex != 0);
 116
 117     int errorcode = pthread_mutex_lock(mutex);
 118     return errorcode == 0;
 119   }
 120   return false;
 121 }
 122
 123 bool
 124 Mutex::release()
 125 {
 126   if (pthread_enabled)
 127   {
 128     pthread_mutex_t* mutex = reinterpret_cast<pthread_mutex_t*>(data_);
 129     assert(mutex != 0);
 130
 131     int errorcode = pthread_mutex_unlock(mutex);
 132     return errorcode == 0;
 133   }
 134   return false;
 135 }
 136
 137 bool
 138 Mutex::tryacquire()
 139 {
 140   if (pthread_enabled)
 141   {
 142     pthread_mutex_t* mutex = reinterpret_cast<pthread_mutex_t*>(data_);
 143     assert(mutex != 0);
 144
 145     int errorcode = pthread_mutex_trylock(mutex);
 146     return errorcode == 0;
 147   }
 148   return false;
 149 }
 150
 151 }
 152
 153 #elif defined(LLVM_ON_UNIX)
 154 #include "Unix/Mutex.inc"
 155 #elif defined( LLVM_ON_WIN32)
 156 #include "Win32/Mutex.inc"
 157 #else
 158 #warning Neither LLVM_ON_UNIX nor LLVM_ON_WIN32 was set in System/Mutex.cpp
 159 #endif
 160 #endif
 161
 162 DEFINING_FILE_FOR(SystemMutex)