How to determine whether a thread exists in Linux

In mysql, you can use the "pthread_kill()" function to determine whether a thread exists. This function can send a sig signal to the thread with a specified ID to determine whether the thread is still alive. The syntax is "int pthread_kill(pthread_t thread, int sig)".

#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.

How to determine whether a thread exists in Linux

pthread_kill:

Don’t be scared by the name, pthread_kill is not kill, but sends a signal to the thread. Remember signal? The default action of most signals is to terminate the running of the process, so we have to use signal() to catch the signal and add a processing function.

int pthread_kill(pthread_t thread, int sig);

Send the sig signal to the thread with the specified ID. If it is not processed in the thread code, the entire process will be affected according to the default behavior of the signal. In other words, if you send SIGQUIT to a thread, but the thread does not If the signal processing function is not implemented, the entire process exits.

The same goes for pthread_kill(threadid, SIGKILL), which kills the entire process.

If you want to get the correct behavior, you need to implement signal(SIGKILL, sig_handler) in the thread.

So, if the parameter of int sig is not 0, you must know exactly what to do, and you must implement the signal processing function of the thread, otherwise, it will affect the entire process.

OK, if int sig is 0, this is a reserved signal, and its function is to determine whether the thread is still alive.

Let’s take a look at the return value of pthread_kill:

• Success: 0

• The thread does not exist: ESRCH

• Illegal signal: EINVAL

So, pthread_kill(threadid,0) is very useful.

The above code can determine whether the thread is still alive.

Related recommendations: "Linux Video Tutorial"

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