CODEWITHSUNDEEP
linuxmultithreadingpthreadssignals
brooks94
brooks94

Reputation: 3936

Delivery of signal to mulitithreaded program with sigmask

If I have a program that has N running threads, and N-1 of them block delivery of the SIGUSR1 signal using pthread_sigmask:

int rc;
sigset_t signal_mask;
sigemptyset(&signal_mask);
sigaddset(&signal_mask, SIGUSR1);
rc = pthread_sigmask(SIG_BLOCK, &signal_mask, NULL);
if (rc != 0) {
  // handle error
}

When the OS (Linux, recent kernel) delivers SIGUSR1 to the process, is it guaranteed to be delivered to the unblocked thread? Or could it, for example, try some subset of the blocked threads and then give up?

Upvotes: 1

Views: 663

Answers (1)

caf
caf

Reputation: 239151

Yes, it is guaranteed that a process-directed signal will be delivered to one of the threads that has it unblocked (if there are any). The relevant quote from POSIX Signal Generation and Delivery:

Signals generated for the process shall be delivered to exactly one of those threads within the process which is in a call to a sigwait() function selecting that signal or has not blocked delivery of the signal.

Upvotes: 1

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