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1 //===----------------------------- Registers.hpp --------------------------===//
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2 //
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3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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4 // See https://llvm.org/LICENSE.txt for license information.
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5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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6 //
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7 //
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8 // Abstract interface to shared reader/writer log, hiding platform and
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9 // configuration differences.
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10 //
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11 //===----------------------------------------------------------------------===//
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12
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13 #ifndef __RWMUTEX_HPP__
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14 #define __RWMUTEX_HPP__
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15
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16 #if defined(_WIN32)
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17 #include <windows.h>
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18 #elif !defined(_LIBUNWIND_HAS_NO_THREADS)
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19 #include <pthread.h>
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20 #if defined(__ELF__) && defined(_LIBUNWIND_LINK_PTHREAD_LIB)
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21 #pragma comment(lib, "pthread")
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22 #endif
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23 #endif
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24
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25 namespace libunwind {
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26
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27 #if defined(_LIBUNWIND_HAS_NO_THREADS)
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28
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29 class _LIBUNWIND_HIDDEN RWMutex {
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30 public:
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31 bool lock_shared() { return true; }
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32 bool unlock_shared() { return true; }
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33 bool lock() { return true; }
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34 bool unlock() { return true; }
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35 };
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36
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37 #elif defined(_WIN32)
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38
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39 class _LIBUNWIND_HIDDEN RWMutex {
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40 public:
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41 bool lock_shared() {
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42 AcquireSRWLockShared(&_lock);
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43 return true;
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44 }
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45 bool unlock_shared() {
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46 ReleaseSRWLockShared(&_lock);
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47 return true;
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48 }
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49 bool lock() {
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50 AcquireSRWLockExclusive(&_lock);
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51 return true;
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52 }
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53 bool unlock() {
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54 ReleaseSRWLockExclusive(&_lock);
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55 return true;
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56 }
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57
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58 private:
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59 SRWLOCK _lock = SRWLOCK_INIT;
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60 };
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61
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62 #elif !defined(LIBUNWIND_USE_WEAK_PTHREAD)
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63
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64 class _LIBUNWIND_HIDDEN RWMutex {
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65 public:
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66 bool lock_shared() { return pthread_rwlock_rdlock(&_lock) == 0; }
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67 bool unlock_shared() { return pthread_rwlock_unlock(&_lock) == 0; }
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68 bool lock() { return pthread_rwlock_wrlock(&_lock) == 0; }
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69 bool unlock() { return pthread_rwlock_unlock(&_lock) == 0; }
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70
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71 private:
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72 pthread_rwlock_t _lock = PTHREAD_RWLOCK_INITIALIZER;
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73 };
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74
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75 #else
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76
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77 extern "C" int __attribute__((weak))
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78 pthread_create(pthread_t *thread, const pthread_attr_t *attr,
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79 void *(*start_routine)(void *), void *arg);
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80 extern "C" int __attribute__((weak))
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81 pthread_rwlock_rdlock(pthread_rwlock_t *lock);
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82 extern "C" int __attribute__((weak))
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83 pthread_rwlock_wrlock(pthread_rwlock_t *lock);
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84 extern "C" int __attribute__((weak))
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85 pthread_rwlock_unlock(pthread_rwlock_t *lock);
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86
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87 // Calls to the locking functions are gated on pthread_create, and not the
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88 // functions themselves, because the data structure should only be locked if
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89 // another thread has been created. This is what similar libraries do.
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90
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91 class _LIBUNWIND_HIDDEN RWMutex {
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92 public:
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93 bool lock_shared() {
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94 return !pthread_create || (pthread_rwlock_rdlock(&_lock) == 0);
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95 }
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96 bool unlock_shared() {
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97 return !pthread_create || (pthread_rwlock_unlock(&_lock) == 0);
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98 }
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99 bool lock() {
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100 return !pthread_create || (pthread_rwlock_wrlock(&_lock) == 0);
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101 }
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102 bool unlock() {
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103 return !pthread_create || (pthread_rwlock_unlock(&_lock) == 0);
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104 }
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105
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106 private:
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107 pthread_rwlock_t _lock = PTHREAD_RWLOCK_INITIALIZER;
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108 };
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109
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110 #endif
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111
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112 } // namespace libunwind
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113
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114 #endif // __RWMUTEX_HPP__
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