1*4684ddb6SLionel Sambuc //===---------------------- shared_mutex.cpp ------------------------------===// 2*4684ddb6SLionel Sambuc // 3*4684ddb6SLionel Sambuc // The LLVM Compiler Infrastructure 4*4684ddb6SLionel Sambuc // 5*4684ddb6SLionel Sambuc // This file is dual licensed under the MIT and the University of Illinois Open 6*4684ddb6SLionel Sambuc // Source Licenses. See LICENSE.TXT for details. 7*4684ddb6SLionel Sambuc // 8*4684ddb6SLionel Sambuc //===----------------------------------------------------------------------===// 9*4684ddb6SLionel Sambuc 10*4684ddb6SLionel Sambuc #define _LIBCPP_BUILDING_SHARED_MUTEX 11*4684ddb6SLionel Sambuc #include "shared_mutex" 12*4684ddb6SLionel Sambuc 13*4684ddb6SLionel Sambuc _LIBCPP_BEGIN_NAMESPACE_STD 14*4684ddb6SLionel Sambuc 15*4684ddb6SLionel Sambuc shared_mutex::shared_mutex() 16*4684ddb6SLionel Sambuc : __state_(0) 17*4684ddb6SLionel Sambuc { 18*4684ddb6SLionel Sambuc } 19*4684ddb6SLionel Sambuc 20*4684ddb6SLionel Sambuc // Exclusive ownership 21*4684ddb6SLionel Sambuc 22*4684ddb6SLionel Sambuc void 23*4684ddb6SLionel Sambuc shared_mutex::lock() 24*4684ddb6SLionel Sambuc { 25*4684ddb6SLionel Sambuc unique_lock<mutex> lk(__mut_); 26*4684ddb6SLionel Sambuc while (__state_ & __write_entered_) 27*4684ddb6SLionel Sambuc __gate1_.wait(lk); 28*4684ddb6SLionel Sambuc __state_ |= __write_entered_; 29*4684ddb6SLionel Sambuc while (__state_ & __n_readers_) 30*4684ddb6SLionel Sambuc __gate2_.wait(lk); 31*4684ddb6SLionel Sambuc } 32*4684ddb6SLionel Sambuc 33*4684ddb6SLionel Sambuc bool 34*4684ddb6SLionel Sambuc shared_mutex::try_lock() 35*4684ddb6SLionel Sambuc { 36*4684ddb6SLionel Sambuc unique_lock<mutex> lk(__mut_); 37*4684ddb6SLionel Sambuc if (__state_ == 0) 38*4684ddb6SLionel Sambuc { 39*4684ddb6SLionel Sambuc __state_ = __write_entered_; 40*4684ddb6SLionel Sambuc return true; 41*4684ddb6SLionel Sambuc } 42*4684ddb6SLionel Sambuc return false; 43*4684ddb6SLionel Sambuc } 44*4684ddb6SLionel Sambuc 45*4684ddb6SLionel Sambuc void 46*4684ddb6SLionel Sambuc shared_mutex::unlock() 47*4684ddb6SLionel Sambuc { 48*4684ddb6SLionel Sambuc lock_guard<mutex> _(__mut_); 49*4684ddb6SLionel Sambuc __state_ = 0; 50*4684ddb6SLionel Sambuc __gate1_.notify_all(); 51*4684ddb6SLionel Sambuc } 52*4684ddb6SLionel Sambuc 53*4684ddb6SLionel Sambuc // Shared ownership 54*4684ddb6SLionel Sambuc 55*4684ddb6SLionel Sambuc void 56*4684ddb6SLionel Sambuc shared_mutex::lock_shared() 57*4684ddb6SLionel Sambuc { 58*4684ddb6SLionel Sambuc unique_lock<mutex> lk(__mut_); 59*4684ddb6SLionel Sambuc while ((__state_ & __write_entered_) || (__state_ & __n_readers_) == __n_readers_) 60*4684ddb6SLionel Sambuc __gate1_.wait(lk); 61*4684ddb6SLionel Sambuc unsigned num_readers = (__state_ & __n_readers_) + 1; 62*4684ddb6SLionel Sambuc __state_ &= ~__n_readers_; 63*4684ddb6SLionel Sambuc __state_ |= num_readers; 64*4684ddb6SLionel Sambuc } 65*4684ddb6SLionel Sambuc 66*4684ddb6SLionel Sambuc bool 67*4684ddb6SLionel Sambuc shared_mutex::try_lock_shared() 68*4684ddb6SLionel Sambuc { 69*4684ddb6SLionel Sambuc unique_lock<mutex> lk(__mut_); 70*4684ddb6SLionel Sambuc unsigned num_readers = __state_ & __n_readers_; 71*4684ddb6SLionel Sambuc if (!(__state_ & __write_entered_) && num_readers != __n_readers_) 72*4684ddb6SLionel Sambuc { 73*4684ddb6SLionel Sambuc ++num_readers; 74*4684ddb6SLionel Sambuc __state_ &= ~__n_readers_; 75*4684ddb6SLionel Sambuc __state_ |= num_readers; 76*4684ddb6SLionel Sambuc return true; 77*4684ddb6SLionel Sambuc } 78*4684ddb6SLionel Sambuc return false; 79*4684ddb6SLionel Sambuc } 80*4684ddb6SLionel Sambuc 81*4684ddb6SLionel Sambuc void 82*4684ddb6SLionel Sambuc shared_mutex::unlock_shared() 83*4684ddb6SLionel Sambuc { 84*4684ddb6SLionel Sambuc lock_guard<mutex> _(__mut_); 85*4684ddb6SLionel Sambuc unsigned num_readers = (__state_ & __n_readers_) - 1; 86*4684ddb6SLionel Sambuc __state_ &= ~__n_readers_; 87*4684ddb6SLionel Sambuc __state_ |= num_readers; 88*4684ddb6SLionel Sambuc if (__state_ & __write_entered_) 89*4684ddb6SLionel Sambuc { 90*4684ddb6SLionel Sambuc if (num_readers == 0) 91*4684ddb6SLionel Sambuc __gate2_.notify_one(); 92*4684ddb6SLionel Sambuc } 93*4684ddb6SLionel Sambuc else 94*4684ddb6SLionel Sambuc { 95*4684ddb6SLionel Sambuc if (num_readers == __n_readers_ - 1) 96*4684ddb6SLionel Sambuc __gate1_.notify_one(); 97*4684ddb6SLionel Sambuc } 98*4684ddb6SLionel Sambuc } 99*4684ddb6SLionel Sambuc 100*4684ddb6SLionel Sambuc 101*4684ddb6SLionel Sambuc _LIBCPP_END_NAMESPACE_STD 102