[英]Unexplained behavior boost::scoped_lock
我寫在C ++多線程TCP服務器上,用於使用boost:scoped_lock進行同步
連接到服務器后,客戶端凍結。
在gdb中,在調用boost :: mutex :: lock之后,我在pthread_kill中看到了更多線程
(gdb) info thread
277 Thread 808779c00 (LWP 245289330/xgps) 0x0000000802579d5c in poll () at poll.S:3
276 Thread 808779800 (LWP 245289329/xgps) 0x00000008019799bc in pthread_kill () from /lib/libthr.so.3
275 Thread 808779400 (LWP 245289328/xgps) 0x00000008019799bc in pthread_kill () from /lib/libthr.so.3
.....
246 Thread 808c92800 (LWP 245289296/xgps) 0x00000008019799bc in pthread_kill () from /lib/libthr.so.3
245 Thread 808643800 (LWP 245289295/xgps) 0x00000008019799bc in pthread_kill () from /lib/libthr.so.3
244 Thread 808643400 (LWP 245289294/xgps) 0x00000008019799bc in pthread_kill () from /lib/libthr.so.3
243 Thread 806c8f400 (LWP 245289292/xgps) 0x00000008019799bc in pthread_kill () from /lib/libthr.so.3
242 Thread 808643000 (LWP 245286262/xgps) 0x00000008019799bc in pthread_kill () from /lib/libthr.so.3
241 Thread 808c92400 (LWP 245289288/xgps) 0x00000008019799bc in pthread_kill () from /lib/libthr.so.3
[Switching to thread 205 (Thread 80863a000 (LWP 245289251/xgps))]#0 0x00000008019799bc in pthread_kill () from /lib/libthr.so.3
(gdb) where
#0 0x00000008019799bc in pthread_kill () from /lib/libthr.so.3
#1 0x0000000801973cfc in pthread_getschedparam () from /lib/libthr.so.3
#2 0x00000008019782fc in pthread_mutex_getprioceiling () from /lib/libthr.so.3
#3 0x000000080197838b in pthread_mutex_lock () from /lib/libthr.so.3
#4 0x0000000000442b2e in boost::mutex::lock (this=0x803835f10) at mutex.hpp:62
#5 0x0000000000442c36 in boost::unique_lock<boost::mutex>::lock (this=0x7fffe7334270) at lock_types.hpp:346
#6 0x0000000000442c7c in unique_lock (this=0x7fffe7334270, m_=@0x803835f10) at lock_types.hpp:124
#7 0x0000000000466e31 in XDevice::getDeviceIMEI (this=0x803835e20) at /home/xgps_app/device.cpp:639
#8 0x000000000049071f in XDevicePool::get_device (this=0x7fffffffd9c0, device_imei=868683024674230) at /home/xgps_app/pool_devices.cpp:351
行device.cpp上的代碼:639
IMEI
XDevice::getDeviceIMEI()
{
try {
boost::mutex::scoped_lock lock(cn_mutex);
return device_imei;
}
catch (std::exception &e )
{
cout << " ERROR in getDeviceIMEI " << e.what() << "\n";
}
return 0;
}
pool_device中的代碼
XDevicePtr
XDevicePool::get_device(IMEI device_imei)
{
XDevicePtr device;
unsigned int i = 0;
while(i < this->devices.size())
{
device = devices[i];
if (device->getDeviceIMEI() == device_imei) {
LOG4CPLUS_DEBUG(logger, "XDevicePool::get_device found!");
return device;
}
i++;
}
device.reset();
return device;
}
XDevicePtr
XDevicePool::get_device_mt(IMEI device_imei)
{
try
{
boost::mutex::scoped_lock lock(pool_mutex);
}
catch (std::exception & e)
{
LOG4CPLUS_ERROR(logger, "XDevicePool::get_device error! " << e.what());
}
// boost::mutex::scoped_lock lock(pool_mutex);
return get_device(device_imei);
}
為什么在調用互斥鎖線程后終止? 我認為死鎖不是這種行為的原因,請幫忙!
tl; dr pthread_kill
可能是一個紅色鯡魚。
為什么在調用互斥鎖線程后終止?
沒有。 您的線程尚未終止(據證明它們仍出現在info thread
)。
您似乎假設pthread_kill
殺死了當前線程。 實際上, pthread_kill
所做的是向另一個線程發送信號。 甚至發送也是可選的(如果sig=0
)。
有關更多詳細信息,請參見手冊頁 。
您有多個鎖。
只要您有多個可能同時需要的鎖,就需要以固定的順序獲取它們,以避免死鎖。
您似乎很可能發生了這種僵局。 請參閱Boost Thread的免費功能boost::lock
http://www.boost.org/doc/libs/1_63_0/doc/html/thread/synchronization.html#thread.synchronization.lock_functions.lock_multiple以幫助以可靠的順序獲取多個鎖。
您還將想要了解std::defer_lock
。
除此之外,多線程程序中的fork
可能會產生干擾。 我認為這超出了現在的解釋范圍,除非您確實在流程中使用了fork
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