posix: signal: implement sigprocmask()

[ycsin]

Implement sigprocmask() by simply redirecting call to the pthread_sigmask() as they are identical in single threaded application.

Fixes #66928

[moonlight83340]

Just want to understand well that part :

/* this should probably go into signal.c but we need access to the lock */
int pthread_sigmask(int how, const sigset_t *ZRESTRICT set, sigset_t *ZRESTRICT oset)
{
	struct posix_thread *t;

	if (!(how == SIG_BLOCK || how == SIG_SETMASK || how == SIG_UNBLOCK)) {
		return EINVAL;
	}

	t = to_posix_thread(pthread_self());
	if (t == NULL) {
		return ESRCH;
	}

	K_SPINLOCK(&pthread_pool_lock) {
		if (oset != NULL) {
			*oset = t->sigset;
		}

		if (set == NULL) {
			K_SPINLOCK_BREAK;
		}

		switch (how) {
		case SIG_BLOCK:
			for (size_t i = 0; i < ARRAY_SIZE(set->sig); ++i) {
				t->sigset.sig[i] |= set->sig[i];
			}
			break;
		case SIG_SETMASK:
			t->sigset = *set;
			break;
		case SIG_UNBLOCK:
			for (size_t i = 0; i < ARRAY_SIZE(set->sig); ++i) {
				t->sigset.sig[i] &= ~set->sig[i];
			}
			break;
		}
	}

	return 0;
}

Could we move the nonlock part on the signal file and apply the block part from thread fonction ?

/* this should probably go into signal.c but we need access to the lock */
int sigmask(int how, const sigset_t *ZRESTRICT set, sigset_t *ZRESTRICT oset)
{
	struct posix_thread *t;

	if (!(how == SIG_BLOCK || how == SIG_SETMASK || how == SIG_UNBLOCK)) {
		return EINVAL;
	}

	t = to_posix_thread(pthread_self());
	if (t == NULL) {
		return ESRCH;
	}

       pthread_lockPartFunction(struct posix_thread *t,int how, const sigset_t *ZRESTRICT set, sigset_t *ZRESTRICT oset);

	return 0;
}

I want to write it to understand and now I writed it, it sounds so bad 😂

[cfriedt]

A temporary nak for the moment because sigprocmask() should only be used with a single-threaded process.

In Zephyr, even with the approximation that we are running in a single process environment, it is (normally) a multi-threaded environment.

This might need to check a Kconfig variable CONFIG_MULTITHREADED before calling into pthread_sigmask().

Likely if CONFIG_MULTITHREADED is chosen, and this function is called, it might need to assert, since it's "unspecified" according to the spec.

https://pubs.opengroup.org/onlinepubs/9699919799/functions/sigprocmask.html

[cfriedt]

This is cool 👍