lib/Support/RWMutex.cpp

   1 //===- RWMutex.cpp - Reader/Writer 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::RWMutex class.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Support/Allocator.h"
  15 #include "llvm/Support/RWMutex.h"
  16 #include "llvm/Config/config.h"
  17
  18 //===----------------------------------------------------------------------===//
  19 //=== WARNING: Implementation here must contain only TRULY operating system
  20 //===          independent code.
  21 //===----------------------------------------------------------------------===//
  22
  23 #if !defined(LLVM_ENABLE_THREADS) || LLVM_ENABLE_THREADS == 0
  24 // Define all methods as no-ops if threading is explicitly disabled
  25
  26 using namespace llvm;
  27 using namespace sys;
  28
  29 RWMutexImpl::RWMutexImpl() = default;
  30 RWMutexImpl::~RWMutexImpl() = default;
  31
  32 bool RWMutexImpl::reader_acquire() { return true; }
  33 bool RWMutexImpl::reader_release() { return true; }
  34 bool RWMutexImpl::writer_acquire() { return true; }
  35 bool RWMutexImpl::writer_release() { return true; }
  36
  37 #else
  38
  39 #if defined(HAVE_PTHREAD_H) && defined(HAVE_PTHREAD_RWLOCK_INIT)
  40
  41 #include <cassert>
  42 #include <cstdlib>
  43 #include <pthread.h>
  44
  45 using namespace llvm;
  46 using namespace sys;
  47
  48 // Construct a RWMutex using pthread calls
  49 RWMutexImpl::RWMutexImpl()
  50 {
  51   // Declare the pthread_rwlock data structures
  52   pthread_rwlock_t* rwlock =
  53     static_cast<pthread_rwlock_t*>(safe_malloc(sizeof(pthread_rwlock_t)));
  54
  55 #ifdef __APPLE__
  56   // Workaround a bug/mis-feature in Darwin's pthread_rwlock_init.
  57   bzero(rwlock, sizeof(pthread_rwlock_t));
  58 #endif
  59
  60   // Initialize the rwlock
  61   int errorcode = pthread_rwlock_init(rwlock, nullptr);
  62   (void)errorcode;
  63   assert(errorcode == 0);
  64
  65   // Assign the data member
  66   data_ = rwlock;
  67 }
  68
  69 // Destruct a RWMutex
  70 RWMutexImpl::~RWMutexImpl()
  71 {
  72   pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  73   assert(rwlock != nullptr);
  74   pthread_rwlock_destroy(rwlock);
  75   free(rwlock);
  76 }
  77
  78 bool
  79 RWMutexImpl::reader_acquire()
  80 {
  81   pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  82   assert(rwlock != nullptr);
  83
  84   int errorcode = pthread_rwlock_rdlock(rwlock);
  85   return errorcode == 0;
  86 }
  87
  88 bool
  89 RWMutexImpl::reader_release()
  90 {
  91   pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  92   assert(rwlock != nullptr);
  93
  94   int errorcode = pthread_rwlock_unlock(rwlock);
  95   return errorcode == 0;
  96 }
  97
  98 bool
  99 RWMutexImpl::writer_acquire()
 100 {
 101   pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
 102   assert(rwlock != nullptr);
 103
 104   int errorcode = pthread_rwlock_wrlock(rwlock);
 105   return errorcode == 0;
 106 }
 107
 108 bool
 109 RWMutexImpl::writer_release()
 110 {
 111   pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
 112   assert(rwlock != nullptr);
 113
 114   int errorcode = pthread_rwlock_unlock(rwlock);
 115   return errorcode == 0;
 116 }
 117
 118 #elif defined(LLVM_ON_UNIX)
 119 #include "Unix/RWMutex.inc"
 120 #elif defined( _WIN32)
 121 #include "Windows/RWMutex.inc"
 122 #else
 123 #warning Neither LLVM_ON_UNIX nor _WIN32 was set in Support/Mutex.cpp
 124 #endif
 125 #endif