gistfile1.txt

#include <boost/thread.hpp> 
#include <iostream>
int main() 
{ 
	boost::shared_mutex mutex;
	
	std::cerr <<"many shared locks!\n";
	boost::shared_lock<boost::shared_mutex> slock1(mutex);
	boost::shared_lock<boost::shared_mutex> slock2(mutex);
	boost::shared_lock<boost::shared_mutex> slock3(mutex);
	boost::shared_lock<boost::shared_mutex> slock4(mutex);
	boost::shared_lock<boost::shared_mutex> slock5(mutex);

	std::cerr <<"get upgrade_lock lock\n";
	boost::upgrade_lock<boost::shared_mutex> wlock(mutex); // write lock

	// boost::upgrade_lock<boost::shared_mutex> write_lock(mutex); // upgrade_lock同士は共存できないので確保不能
	// boost::upgrade_to_unique_lock<boost::shared_mutex> write_lock(wlock); // shared_lockが全部開放されるまで確保不能

	boost::shared_lock<boost::shared_mutex> slock6(mutex); // shared_lockは追加で獲得可能

	std::cerr <<"end\n"; // shared_lockとupgrade_lockは共存できるのでこのプログラムはendと出力して終了する
}