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
9#include <mutex>
10#include <shared_mutex>
11#if defined(__ELF__) && defined(_LIBCPP_LINK_PTHREAD_LIB)
12# pragma comment(lib, "pthread")
13#endif
14
15_LIBCPP_BEGIN_NAMESPACE_STD
16
17// Shared Mutex Base
18__shared_mutex_base::__shared_mutex_base() : __state_(0) {}
19
20// Exclusive ownership
21
22void __shared_mutex_base::lock() {
23 unique_lock<mutex> lk(__mut_);
24 while (__state_ & __write_entered_)
25 __gate1_.wait(lk&: lk);
26 __state_ |= __write_entered_;
27 while (__state_ & __n_readers_)
28 __gate2_.wait(lk&: lk);
29}
30
31bool __shared_mutex_base::try_lock() {
32 unique_lock<mutex> lk(__mut_);
33 if (__state_ == 0) {
34 __state_ = __write_entered_;
35 return true;
36 }
37 return false;
38}
39
40void __shared_mutex_base::unlock() {
41 {
42 lock_guard<mutex> _(__mut_);
43 __state_ = 0;
44 }
45 __gate1_.notify_all();
46}
47
48// Shared ownership
49
50void __shared_mutex_base::lock_shared() {
51 unique_lock<mutex> lk(__mut_);
52 while ((__state_ & __write_entered_) || (__state_ & __n_readers_) == __n_readers_)
53 __gate1_.wait(lk&: lk);
54 unsigned num_readers = (__state_ & __n_readers_) + 1;
55 __state_ &= ~__n_readers_;
56 __state_ |= num_readers;
57}
58
59bool __shared_mutex_base::try_lock_shared() {
60 unique_lock<mutex> lk(__mut_);
61 unsigned num_readers = __state_ & __n_readers_;
62 if (!(__state_ & __write_entered_) && num_readers != __n_readers_) {
63 ++num_readers;
64 __state_ &= ~__n_readers_;
65 __state_ |= num_readers;
66 return true;
67 }
68 return false;
69}
70
71void __shared_mutex_base::unlock_shared() {
72 unique_lock<mutex> lk(__mut_);
73 unsigned num_readers = (__state_ & __n_readers_) - 1;
74 __state_ &= ~__n_readers_;
75 __state_ |= num_readers;
76 if (__state_ & __write_entered_) {
77 if (num_readers == 0) {
78 lk.unlock();
79 __gate2_.notify_one();
80 }
81 } else {
82 if (num_readers == __n_readers_ - 1) {
83 lk.unlock();
84 __gate1_.notify_one();
85 }
86 }
87}
88
89// Shared Timed Mutex
90// These routines are here for ABI stability
91shared_timed_mutex::shared_timed_mutex() : __base_() {}
92void shared_timed_mutex::lock() { return __base_.lock(); }
93bool shared_timed_mutex::try_lock() { return __base_.try_lock(); }
94void shared_timed_mutex::unlock() { return __base_.unlock(); }
95void shared_timed_mutex::lock_shared() { return __base_.lock_shared(); }
96bool shared_timed_mutex::try_lock_shared() { return __base_.try_lock_shared(); }
97void shared_timed_mutex::unlock_shared() { return __base_.unlock_shared(); }
98
99_LIBCPP_END_NAMESPACE_STD
100