int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
{
	struct task_struct *p = current, *t;
	struct k_sigaction *k;
	sigset_t mask;

	if (!valid_signal(sig) || sig < 1 || (act && sig_kernel_only(sig)))
		return -EINVAL;

	k = &p->sighand->action[sig-1];

	spin_lock_irq(&p->sighand->siglock);
	if (oact)
		*oact = *k;

	sigaction_compat_abi(act, oact);

	if (act) {
		sigdelsetmask(&act->sa.sa_mask,
			      sigmask(SIGKILL) | sigmask(SIGSTOP));
		*k = *act;
		/*
		 * POSIX 3.3.1.3:
		 *  "Setting a signal action to SIG_IGN for a signal that is
		 *   pending shall cause the pending signal to be discarded,
		 *   whether or not it is blocked."
		 *
		 *  "Setting a signal action to SIG_DFL for a signal that is
		 *   pending and whose default action is to ignore the signal
		 *   (for example, SIGCHLD), shall cause the pending signal to
		 *   be discarded, whether or not it is blocked"
		 */
		if (sig_handler_ignored(sig_handler(p, sig), sig)) {
			sigemptyset(&mask);
			sigaddset(&mask, sig);
			flush_sigqueue_mask(&mask, &p->signal->shared_pending);
			for_each_thread(p, t)
				flush_sigqueue_mask(&mask, &t->pending);
		}
	}

	spin_unlock_irq(&p->sighand->siglock);
	return 0;
}