Synchronization of QT multithreading

In writing today qt There was a problem in the process of the program . My program theoretically has two threads , But it's not at all . In addition to the main thread, my other thread's main task is to listen to a network port , After receiving the data, send it to the main thread in the form of a signal , Then the main thread processes the corresponding data in the corresponding slot function . At the same time, my main thread also handles many key slot functions , A zero hour dialog window will pop up in the slot function of the key . My problem is when I deal with the pop-up window of the key slot function （ Note that the key slot function has not returned ） The signal sent by the network monitoring thread to the main thread is received on site and enters the corresponding slot function for processing , At this time, the program is stuck . For a professional software engineer , This situation is absolutely not allowed to happen . Based on years of multi-threaded programming experience, I immediately realized the problem （ It is the process described above ）. Obviously, this is a typical thread synchronization often encountered in multithreaded programs （ A critical region ） The problem of . Obviously, the code behind the pop-up window is not allowed to be interrupted , We need to protect this part of code as critical area code . So I tried this method , But this method is invalid . So I looked at qt Official documents of , I found the QObject：：connect The role of the fifth parameter of the function ：

connect(Sender,SIGNAL(signal),Receiver,SLOT(slot),Qt::DirectConnection);  
 The fifth parameter represents the thread in which the slot function is executed  ：
1) Auto connect (AutoConnection), Default connection mode , If the signal is connected to the slot , That is, the sender and the receiver are on the same thread , Equivalent to direct connection ; If the sender and receiver are in different threads , Equivalent to a queue connection .
2) Direct connection (DirectConnection), When the signal is transmitted , The slot function immediately calls . No matter which thread the slot function belongs to , Slot functions are always executed on the sender's thread , That is, the slot function and the sender are on the same thread 
3) Queue connection (QueuedConnection), When control returns to the event loop of the recipient's thread , The slot function is called . The thread receiver is in the function execution slot , That is, the slot function and the signal receiver are in the same thread 
4) Lock queue connection (QueuedConnection)
Qt::BlockingQueuedConnection： The call timing of the slot function is the same as Qt::QueuedConnection Agreement , However, after sending the signal, the sender's thread will block , Until the slot function runs . The receiver and sender must not be in the same thread , Otherwise the program will deadlock . This may be required when synchronization is required between multiple threads .
5) Single connection (UniqueConnection)
Qt::UniqueConnection： This flag It can be done by biting or （|） Used in combination with the above four . When this flag When setting , When a signal is connected to a slot , Repeated connections will fail . That is to avoid repeated connections 

therefore , According to the actual application scenario , I used the signal slot function of the network monitoring thread QueuedConnection, Then there is no jam .