/* $Id: fast_sigblock.c,v 1.2 2013/01/09 07:32:04 kostik Exp $ */

#include <sys/types.h>
#include <sys/signalvar.h>
#include <sys/syscall.h>
#include <err.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <machine/atomic.h>

#ifndef FAST_SIGBLOCK_PEND
#define	FAST_SIGBLOCK_SETPTR	1
#define	FAST_SIGBLOCK_UNBLOCK	2
#define	FAST_SIGBLOCK_UNSETPTR	3

#define	FAST_SIGBLOCK_PEND	0x1
#define	FAST_SIGBLOCK_INC	0x10

#define	SYS_fast_sigblock	533
#endif

static uint32_t fsigblock;
static int cnt;

static int
killer(void *arg)
{
	static const char a[] = ".";
	pid_t worker_pid;
	int error, oldcnt, mcnt;

	worker_pid = *(pid_t *)arg;
	oldcnt = cnt;
	for (;;) {
		error = kill(worker_pid, SIGHUP);
		if (error != 0)
			errc(1, error, "kill");
		/* usleep(300); */
		mcnt = cnt;
		if (mcnt != oldcnt) {
			oldcnt = mcnt;
			if (mcnt % 100 != 0)
				write(2, a, 1);
		}
	}
	return (0);
}

static void
fast_sigblock_loc(int cmd, uint32_t *ptr)
{
	int error;

	error = syscall(SYS_fast_sigblock, cmd, ptr);
	if (error == -1)
		err(1, "SYS_fast_sigblock");
}

static void
handler(int signo)
{
	static const char a[1] = "!";
	uint32_t fs;

	fs = fsigblock;
	if (fs != 0) {
		printf("sig %d fsigblock %x\n", signo, fs);
		exit(1);
	}
	if (++cnt % 100 == 0)
		write(2, a, 1);
}

static void
worker(void)
{
	uint32_t oldval;

	fast_sigblock_loc(FAST_SIGBLOCK_SETPTR, &fsigblock);
	for (;;) {
		atomic_add_int(&fsigblock, FAST_SIGBLOCK_INC);
		/* usleep(700); */
		oldval = atomic_fetchadd_int(&fsigblock, -FAST_SIGBLOCK_INC);
		if (oldval == (FAST_SIGBLOCK_PEND | FAST_SIGBLOCK_INC))
			fast_sigblock_loc(FAST_SIGBLOCK_UNBLOCK, NULL);
	}
}

int
main(void)
{
	struct sigaction sa;
	char *stack;
	pid_t my_pid, killer_pid;

	bzero(&sa, sizeof(sa));
	sa.sa_handler = handler;
	if (sigaction(SIGHUP, &sa, NULL) == -1)
		err(1, "sigaction");

	stack = malloc(100 * getpagesize());
	my_pid = getpid();
	killer_pid = rfork_thread(RFPROC | RFMEM, stack, killer, &my_pid);
	if (killer_pid == -1)
		err(1, "rfork_thread");
	worker();

	return (0);
}