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