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/Config/config.h"
  15 #include "llvm/Support/RWMutex.h"
  16 #include <cstring>
  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 namespace llvm {
  26 using namespace sys;
  27 RWMutexImpl::RWMutexImpl() { }
  28 RWMutexImpl::~RWMutexImpl() { }
  29 bool RWMutexImpl::reader_acquire() { return true; }
  30 bool RWMutexImpl::reader_release() { return true; }
  31 bool RWMutexImpl::writer_acquire() { return true; }
  32 bool RWMutexImpl::writer_release() { return true; }
  33 }
  34 #else
  35
  36 #if defined(HAVE_PTHREAD_H) && defined(HAVE_PTHREAD_RWLOCK_INIT)
  37
  38 #include <cassert>
  39 #include <pthread.h>
  40 #include <stdlib.h>
  41
  42 namespace llvm {
  43 using namespace sys;
  44
  45 // Construct a RWMutex using pthread calls
  46 RWMutexImpl::RWMutexImpl()
  47   : data_(nullptr)
  48 {
  49   // Declare the pthread_rwlock data structures
  50   pthread_rwlock_t* rwlock =
  51     static_cast<pthread_rwlock_t*>(malloc(sizeof(pthread_rwlock_t)));
  52
  53 #ifdef __APPLE__
  54   // Workaround a bug/mis-feature in Darwin's pthread_rwlock_init.
  55   bzero(rwlock, sizeof(pthread_rwlock_t));
  56 #endif
  57
  58   // Initialize the rwlock
  59   int errorcode = pthread_rwlock_init(rwlock, nullptr);
  60   (void)errorcode;
  61   assert(errorcode == 0);
  62
  63   // Assign the data member
  64   data_ = rwlock;
  65 }
  66
  67 // Destruct a RWMutex
  68 RWMutexImpl::~RWMutexImpl()
  69 {
  70   pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  71   assert(rwlock != nullptr);
  72   pthread_rwlock_destroy(rwlock);
  73   free(rwlock);
  74 }
  75
  76 bool
  77 RWMutexImpl::reader_acquire()
  78 {
  79   pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  80   assert(rwlock != nullptr);
  81
  82   int errorcode = pthread_rwlock_rdlock(rwlock);
  83   return errorcode == 0;
  84 }
  85
  86 bool
  87 RWMutexImpl::reader_release()
  88 {
  89   pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  90   assert(rwlock != nullptr);
  91
  92   int errorcode = pthread_rwlock_unlock(rwlock);
  93   return errorcode == 0;
  94 }
  95
  96 bool
  97 RWMutexImpl::writer_acquire()
  98 {
  99   pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
 100   assert(rwlock != nullptr);
 101
 102   int errorcode = pthread_rwlock_wrlock(rwlock);
 103   return errorcode == 0;
 104 }
 105
 106 bool
 107 RWMutexImpl::writer_release()
 108 {
 109   pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
 110   assert(rwlock != nullptr);
 111
 112   int errorcode = pthread_rwlock_unlock(rwlock);
 113   return errorcode == 0;
 114 }
 115
 116 }
 117
 118 #elif defined(LLVM_ON_UNIX)
 119 #include "Unix/RWMutex.inc"
 120 #elif defined( LLVM_ON_WIN32)
 121 #include "Windows/RWMutex.inc"
 122 #else
 123 #warning Neither LLVM_ON_UNIX nor LLVM_ON_WIN32 was set in Support/Mutex.cpp
 124 #endif
 125 #endif