1//===----------------------------------------------------------------------===//
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// Abstract interface to shared reader/writer log, hiding platform and
9// configuration differences.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef __RWMUTEX_HPP__
14#define __RWMUTEX_HPP__
15
16#if defined(_WIN32)
17#include <windows.h>
18#elif !defined(_LIBUNWIND_HAS_NO_THREADS)
19#include <pthread.h>
20#if defined(__ELF__) && defined(_LIBUNWIND_LINK_PTHREAD_LIB)
21#pragma comment(lib, "pthread")
22#endif
23#endif
24
25namespace libunwind {
26
27#if defined(_LIBUNWIND_HAS_NO_THREADS)
28
29class _LIBUNWIND_HIDDEN RWMutex {
30public:
31 bool lock_shared() { return true; }
32 bool unlock_shared() { return true; }
33 bool lock() { return true; }
34 bool unlock() { return true; }
35};
36
37#elif defined(_WIN32)
38
39class _LIBUNWIND_HIDDEN RWMutex {
40public:
41 bool lock_shared() {
42 AcquireSRWLockShared(&_lock);
43 return true;
44 }
45 bool unlock_shared() {
46 ReleaseSRWLockShared(&_lock);
47 return true;
48 }
49 bool lock() {
50 AcquireSRWLockExclusive(&_lock);
51 return true;
52 }
53 bool unlock() {
54 ReleaseSRWLockExclusive(&_lock);
55 return true;
56 }
57
58private:
59 SRWLOCK _lock = SRWLOCK_INIT;
60};
61
62#elif !defined(LIBUNWIND_USE_WEAK_PTHREAD)
63
64class _LIBUNWIND_HIDDEN RWMutex {
65public:
66 bool lock_shared() { return pthread_rwlock_rdlock(rwlock: &_lock) == 0; }
67 bool unlock_shared() { return pthread_rwlock_unlock(rwlock: &_lock) == 0; }
68 bool lock() { return pthread_rwlock_wrlock(rwlock: &_lock) == 0; }
69 bool unlock() { return pthread_rwlock_unlock(rwlock: &_lock) == 0; }
70
71private:
72 pthread_rwlock_t _lock = PTHREAD_RWLOCK_INITIALIZER;
73};
74
75#else
76
77extern "C" int __attribute__((weak))
78pthread_create(pthread_t *thread, const pthread_attr_t *attr,
79 void *(*start_routine)(void *), void *arg);
80extern "C" int __attribute__((weak))
81pthread_rwlock_rdlock(pthread_rwlock_t *lock);
82extern "C" int __attribute__((weak))
83pthread_rwlock_wrlock(pthread_rwlock_t *lock);
84extern "C" int __attribute__((weak))
85pthread_rwlock_unlock(pthread_rwlock_t *lock);
86
87// Calls to the locking functions are gated on pthread_create, and not the
88// functions themselves, because the data structure should only be locked if
89// another thread has been created. This is what similar libraries do.
90
91class _LIBUNWIND_HIDDEN RWMutex {
92public:
93 bool lock_shared() {
94 return !pthread_create || (pthread_rwlock_rdlock(&_lock) == 0);
95 }
96 bool unlock_shared() {
97 return !pthread_create || (pthread_rwlock_unlock(&_lock) == 0);
98 }
99 bool lock() {
100 return !pthread_create || (pthread_rwlock_wrlock(&_lock) == 0);
101 }
102 bool unlock() {
103 return !pthread_create || (pthread_rwlock_unlock(&_lock) == 0);
104 }
105
106private:
107 pthread_rwlock_t _lock = PTHREAD_RWLOCK_INITIALIZER;
108};
109
110#endif
111
112} // namespace libunwind
113
114#endif // __RWMUTEX_HPP__
115