1 //===---------------------- shared_mutex.cpp ------------------------------===//
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
7 //===----------------------------------------------------------------------===//
10 #ifndef _LIBCPP_HAS_NO_THREADS
12 #include "shared_mutex"
13 #if defined(__ELF__) && defined(_LIBCPP_LINK_PTHREAD_LIB)
14 #pragma comment(lib, "pthread")
17 _LIBCPP_BEGIN_NAMESPACE_STD
20 __shared_mutex_base::__shared_mutex_base()
25 // Exclusive ownership
28 __shared_mutex_base::lock()
30 unique_lock<mutex> lk(__mut_);
31 while (__state_ & __write_entered_)
33 __state_ |= __write_entered_;
34 while (__state_ & __n_readers_)
39 __shared_mutex_base::try_lock()
41 unique_lock<mutex> lk(__mut_);
44 __state_ = __write_entered_;
51 __shared_mutex_base::unlock()
53 lock_guard<mutex> _(__mut_);
55 __gate1_.notify_all();
61 __shared_mutex_base::lock_shared()
63 unique_lock<mutex> lk(__mut_);
64 while ((__state_ & __write_entered_) || (__state_ & __n_readers_) == __n_readers_)
66 unsigned num_readers = (__state_ & __n_readers_) + 1;
67 __state_ &= ~__n_readers_;
68 __state_ |= num_readers;
72 __shared_mutex_base::try_lock_shared()
74 unique_lock<mutex> lk(__mut_);
75 unsigned num_readers = __state_ & __n_readers_;
76 if (!(__state_ & __write_entered_) && num_readers != __n_readers_)
79 __state_ &= ~__n_readers_;
80 __state_ |= num_readers;
87 __shared_mutex_base::unlock_shared()
89 lock_guard<mutex> _(__mut_);
90 unsigned num_readers = (__state_ & __n_readers_) - 1;
91 __state_ &= ~__n_readers_;
92 __state_ |= num_readers;
93 if (__state_ & __write_entered_)
96 __gate2_.notify_one();
100 if (num_readers == __n_readers_ - 1)
101 __gate1_.notify_one();
106 // Shared Timed Mutex
107 // These routines are here for ABI stability
108 shared_timed_mutex::shared_timed_mutex() : __base() {}
109 void shared_timed_mutex::lock() { return __base.lock(); }
110 bool shared_timed_mutex::try_lock() { return __base.try_lock(); }
111 void shared_timed_mutex::unlock() { return __base.unlock(); }
112 void shared_timed_mutex::lock_shared() { return __base.lock_shared(); }
113 bool shared_timed_mutex::try_lock_shared() { return __base.try_lock_shared(); }
114 void shared_timed_mutex::unlock_shared() { return __base.unlock_shared(); }
116 _LIBCPP_END_NAMESPACE_STD
118 #endif // !_LIBCPP_HAS_NO_THREADS