sem_wait interrupt signal on FreeBSD

Question

I have noticed that on my copy of FreeBSD9 the man page for sem_wait from sempahore.h does not have a EINTR error return value. I currently have some code that has a signal handler, and I am raising a SIGINT signal. This does not seem to be waking up my sem_wait() so I can check the return value, thus the thread that is running the function wtih the sem_wait gets hung indefinitely.

According to the linux man page, I should be able to raise the singal, test for the EINTR value in the thread that is doing the sem_wait, but that seems to be missing in FreeBSD.

What is the right way of fixing this?

In psuedo here is what I have

signal_handler() //handles SIGINT
{
loopvar = 0;
}

thread 1:

while(loopvar)
{

    if((r = sem_wait())
    {
    check error value
     continue
    }

    ..
    sem_post()
}

thread 2:

raise(SIGINT);

so I was expecting when thread2 raises SIGINT it will cause sem_wait to return with a value, the loop would continue, but now loopvar would be zero, so I would exit my infinite loop.

edit: to be clear, I am not using the SA_RESTART flag.

Answer 1

raise raises the signal for the calling thread, not for the process. If you want to signal the whole process (with delivery to a random thread that has the signal unmasked), you need the kill function. If you want to signal a specific thread, you need pthread_kill .