lib/Support/RWMutex.cpp

   1 //===- RWMutex.cpp - Reader/Writer Mutual Exclusion Lock --------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements the llvm::sys::RWMutex class.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/Support/Allocator.h"
  14 #include "llvm/Support/RWMutex.h"
  15 #include "llvm/Config/config.h"
  16
  17 #if defined(LLVM_USE_RW_MUTEX_IMPL)
  18 using namespace llvm;
  19 using namespace sys;
  20
  21 #if !defined(LLVM_ENABLE_THREADS) || LLVM_ENABLE_THREADS == 0
  22 // Define all methods as no-ops if threading is explicitly disabled
  23
  24 RWMutexImpl::RWMutexImpl() = default;
  25 RWMutexImpl::~RWMutexImpl() = default;
  26
  27 bool RWMutexImpl::lock_shared() { return true; }
  28 bool RWMutexImpl::unlock_shared() { return true; }
  29 bool RWMutexImpl::lock() { return true; }
  30 bool RWMutexImpl::unlock() { return true; }
  31
  32 #else
  33
  34 #if defined(HAVE_PTHREAD_H) && defined(HAVE_PTHREAD_RWLOCK_INIT)
  35
  36 #include <cassert>
  37 #include <cstdlib>
  38 #include <pthread.h>
  39
  40 // Construct a RWMutex using pthread calls
  41 RWMutexImpl::RWMutexImpl()
  42 {
  43   // Declare the pthread_rwlock data structures
  44   pthread_rwlock_t* rwlock =
  45     static_cast<pthread_rwlock_t*>(safe_malloc(sizeof(pthread_rwlock_t)));
  46
  47 #ifdef __APPLE__
  48   // Workaround a bug/mis-feature in Darwin's pthread_rwlock_init.
  49   bzero(rwlock, sizeof(pthread_rwlock_t));
  50 #endif
  51
  52   // Initialize the rwlock
  53   int errorcode = pthread_rwlock_init(rwlock, nullptr);
  54   (void)errorcode;
  55   assert(errorcode == 0);
  56
  57   // Assign the data member
  58   data_ = rwlock;
  59 }
  60
  61 // Destruct a RWMutex
  62 RWMutexImpl::~RWMutexImpl()
  63 {
  64   pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  65   assert(rwlock != nullptr);
  66   pthread_rwlock_destroy(rwlock);
  67   free(rwlock);
  68 }
  69
  70 bool
  71 RWMutexImpl::lock_shared()
  72 {
  73   pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  74   assert(rwlock != nullptr);
  75
  76   int errorcode = pthread_rwlock_rdlock(rwlock);
  77   return errorcode == 0;
  78 }
  79
  80 bool
  81 RWMutexImpl::unlock_shared()
  82 {
  83   pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  84   assert(rwlock != nullptr);
  85
  86   int errorcode = pthread_rwlock_unlock(rwlock);
  87   return errorcode == 0;
  88 }
  89
  90 bool
  91 RWMutexImpl::lock()
  92 {
  93   pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
  94   assert(rwlock != nullptr);
  95
  96   int errorcode = pthread_rwlock_wrlock(rwlock);
  97   return errorcode == 0;
  98 }
  99
 100 bool
 101 RWMutexImpl::unlock()
 102 {
 103   pthread_rwlock_t* rwlock = static_cast<pthread_rwlock_t*>(data_);
 104   assert(rwlock != nullptr);
 105
 106   int errorcode = pthread_rwlock_unlock(rwlock);
 107   return errorcode == 0;
 108 }
 109
 110 #else
 111
 112 RWMutexImpl::RWMutexImpl() : data_(new MutexImpl(false)) { }
 113
 114 RWMutexImpl::~RWMutexImpl() {
 115   delete static_cast<MutexImpl *>(data_);
 116 }
 117
 118 bool RWMutexImpl::lock_shared() {
 119   return static_cast<MutexImpl *>(data_)->acquire();
 120 }
 121
 122 bool RWMutexImpl::unlock_shared() {
 123   return static_cast<MutexImpl *>(data_)->release();
 124 }
 125
 126 bool RWMutexImpl::lock() {
 127   return static_cast<MutexImpl *>(data_)->acquire();
 128 }
 129
 130 bool RWMutexImpl::unlock() {
 131   return static_cast<MutexImpl *>(data_)->release();
 132 }
 133
 134 #endif
 135 #endif
 136 #endif