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(&_lock) == 0;  }
 67  bool unlock_shared() { return pthread_rwlock_unlock(&_lock) == 0; }
 68  bool lock() { return pthread_rwlock_wrlock(&_lock) == 0; }
 69  bool unlock() { return pthread_rwlock_unlock(&_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__