c++ 递归锁的使用示例代码

#include <iostream>
#include <mutex>
#include <thread>
#include <unistd.h>
using namespace std;
std::mutex m_mutex;
void Func()
{
	m_mutex.lock();
	cout << "Func" << endl;
	m_mutex.unlock();
}
int main()
{
	// create thread
	std::thread th1 = std::thread([&]() {
		while(1)
		{
			m_mutex.lock();
			cout << "thread1 working" << endl;
			Func();
			m_mutex.unlock();
			sleep(1);
		}
	});
	th1.join();	
	while(1)
	{
		sleep(2);
	}
	return 0;
}

[root@localhost ~]# ./testDeadLock
thread1 working

[root@localhost deadLock]# ps -aux | grep testDeadLock
root      88473  0.0  0.1  27200  1156 pts/1    Sl+  14:13   0:00 ./testDeadLock
root      88541  0.0  0.1 112832   996 pts/2    R+   14:13   0:00 grep --color=auto testDeadLock
[root@localhost deadLock]# gdb attach 88473
//... 
(gdb) info threads
  Id   Target Id         Frame 
  2    Thread 0x7f13e4603700 (LWP 88474) "testDeadLock" 0x00007f13e530454d in __lll_lock_wait () from /lib64/libpthread.so.0
* 1    Thread 0x7f13e5a1d740 (LWP 88473) "testDeadLock" 0x00007f13e52ff017 in pthread_join () from /lib64/libpthread.so.0
(gdb) t 2
[Switching to thread 2 (Thread 0x7f13e4603700 (LWP 88474))]
#0  0x00007f13e530454d in __lll_lock_wait () from /lib64/libpthread.so.0
(gdb) bt
#0  0x00007f13e530454d in __lll_lock_wait () from /lib64/libpthread.so.0
#1  0x00007f13e52ffe9b in _L_lock_883 () from /lib64/libpthread.so.0
#2  0x00007f13e52ffd68 in pthread_mutex_lock () from /lib64/libpthread.so.0
#3  0x0000000000402534 in __gthread_mutex_lock (__mutex=0x604120 <m_mutex>) at /opt/rh/devtoolset-8/root/usr/include/c++/8/x86_64-redhat-linux/bits/gthr-default.h:748
#4  0x0000000000402584 in std::mutex::lock (this=0x604120 <m_mutex>) at /opt/rh/devtoolset-8/root/usr/include/c++/8/bits/std_mutex.h:103
#5  0x0000000000401f88 in Func () at source/test.cpp:12
#6  0x000000000040200a in <lambda()>::operator()(void) const (__closure=0x2439018) at source/test.cpp:28
#7  0x0000000000402242 in std::__invoke_impl<void, main()::<lambda()> >(std::__invoke_other, <unknown type in /home/testDeadLock, CU 0x0, DIE 0xada9>) (
    __f=<unknown type in /home/testDeadLock, CU 0x0, DIE 0xada9>) at /opt/rh/devtoolset-8/root/usr/include/c++/8/bits/invoke.h:60
#8  0x000000000040209e in std::__invoke<main()::<lambda()> >(<unknown type in /mnt/hgfs/test/deadLock/debug.x64-linux-g8/testDeadLock, CU 0x0, DIE 0xb073>) (
    __fn=<unknown type in /home/testDeadLock, CU 0x0, DIE 0xb073>) at /opt/rh/devtoolset-8/root/usr/include/c++/8/bits/invoke.h:95
#9  0x0000000000402484 in std::thread::_Invoker<std::tuple<main()::<lambda()> > >::_M_invoke<0>(std::_Index_tuple<0>) (this=0x2439018) at /opt/rh/devtoolset-8/root/usr/include/c++/8/thread:244
#10 0x000000000040245a in std::thread::_Invoker<std::tuple<main()::<lambda()> > >::operator()(void) (this=0x2439018) at /opt/rh/devtoolset-8/root/usr/include/c++/8/thread:253
#11 0x000000000040243e in std::thread::_State_impl<std::thread::_Invoker<std::tuple<main()::<lambda()> > > >::_M_run(void) (this=0x2439010) at /opt/rh/devtoolset-8/root/usr/include/c++/8/thread:196
#12 0x00000000004028ff in execute_native_thread_routine ()
#13 0x00007f13e52fdea5 in start_thread () from /lib64/libpthread.so.0
#14 0x00007f13e4702b0d in clone () from /lib64/libc.so.6
(gdb) f 5
#5  0x0000000000401f88 in Func () at source/test.cpp:12
12		m_mutex.lock();
(gdb) p *(pthread_mutex_t*)$rdi
$1 = {__data = {__lock = 2, __count = 0, __owner = 88474, __nusers = 1, __kind = 0, __spins = 0, __elision = 0, __list = {__prev = 0x0, __next = 0x0}}, 
  __size = "\002\000\000\000\000\000\000\000\232Y\001\000\001", '\000' <repeats 26 times>, __align = 2}
(gdb) 

1) ps查看进程id;
2) "gdb attach 进程id"附加至该进程;
3) "info threads"查看所有线程信息;
4) 查找有执行锁等待__lll_lock_wait ()的线程, 一般为死锁线程, 切换至该线程, 如切换至线程2,则执行"t 2";
5) "bt" 查看当前线程堆栈;
6) "f 帧数"切换至自己所写代码处;
7) "p *(pthread_mutex_t*)$rdi"打印寄存器信息, rdi为显示寄存器;
8) 对7)的打印主要关注两个地方,"__lock = 2"一般说明有死锁, "__owner = 88474"代码发生死锁的线程, 与"info threads"的打印信息中 "(LWP 88474)"对应, 接下来直接分析88474指向的线程即可;

#include <iostream>
#include <mutex>
#include <thread>
#include <unistd.h>
using namespace std;
std::recursive_mutex m_recursive_mutex;
void Func()
{
	std::lock_guard<std::recursive_mutex> mtx(m_recursive_mutex);
	cout << "Func" << endl;
}
int main()
{
	// create thread1
	std::thread th1 = std::thread([&]() {
		while(1)
		{
			std::lock_guard<std::recursive_mutex> mtx(m_recursive_mutex);
			cout << "thread1 working" << endl;
			Func();
			sleep(1);
		}
	});
	th1.join();	
	while(1)
	{
		sleep(2);
	}
	return 0;
}

// 初始化一个临界区对象
void InitializeCriticalSection(  LPCRITICAL_SECTION lpCriticalSection);
// 删除临界区对象释放由该对象使用的所有系统资源
void DeleteCriticalSection(_Inout_ LPCRITICAL_SECTION lpCriticalSection);
// 进入临界区
void EnterCriticalSection( LPCRITICAL_SECTION lpCriticalSection );
// 删除临界区
void LeaveCriticalSection( LPCRITICAL_SECTION lpCriticalSection );

#include <iostream>
#include <thread>
#include <Windows.h>
using namespace std;
CRITICAL_SECTION g_Critical;
class CWinRecursiveLock
{
public:
	CWinRecursiveLock(CRITICAL_SECTION *pCritcal)	
	{
		m_pCritical = pCritcal;
		EnterCriticalSection(m_pCritical);
	}
	~CWinRecursiveLock()	//析构函数
	{
		LeaveCriticalSection(m_pCritical);
	}
private:
	CRITICAL_SECTION *m_pCritical = nullptr;
};
void Func()
{
	CWinRecursiveLock wlock(&g_Critical);  // 重复加锁
	cout << "Func" << endl;
}
int main()
{
	// 初始化
	InitializeCriticalSection(&g_Critical);
	std::thread th1 = std::thread([&]() {
		while(1)
		{
			CWinRecursiveLock wlock(&g_Critical);
			cout << "thread1 working" << endl;
			Func();
			Sleep(1000);
		}
	});
	th1.join();	
	system("pause");
	return 0;
}