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csignalsposixpause

pause() signal handler

The pause() function blocks until a signal arrives. Assuming the process got a signal and pause() returned, does the signal handler will be executed before the code that follows the pause() call, or the result is unexpected?

Example: 

void sigusr1_handler() 
{
   // .. handler code
}

void main() 
{
   // .. bind handler to SIGUSR1

   pause(); // wait for SIGUSR1
   // some more code
}

Does "some more code" will always be executed after sigusr1_handler() has finished, or there is a race condition? If so, what is the solution?
I cannot think of anything besides busy-waiting, but then the pause won't be needed at all..

Solution

  • Citing from the man page for pause(2):

    pause() returns only when a signal was caught and the signal-catching function returned. In this case, pause() returns -1, and errno is set to EINTR.

    You can be sure that your signal handler runs before some more code.