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
126