#include <u.h>
#include <libc.h>

enum{
	Slop	= 100,
	Slop1	= 10,
};

uint	nmiss;
uint	maxmiss;
uint	missmsec;

int
note(void*, char *err)
{
	return strstr(err, "alarm") != nil;
}

void
alarmproc(int ival)
{
	int n;
	long t[2], δt, δ;

	atnotify(note, 1);
	for(n=0;; n++){
		t[0] = nsec()/1000000ull;
		alarm(ival);

		/* evil twist: exit with alarm armed */
		if(n > 150){
			if(nmiss>0)
				fprint(2, 	"nmiss = %d; max = %d; avg = %d\n",
					nmiss, maxmiss, missmsec/nmiss);
			exits("");
		}

		if(sleep(ival*3) != -1){
			print("sleep %d not interrupted: %d\n", n, ival*2);
			continue;
		}
		t[1] = nsec()/1000000ull;
		δt = t[1] - t[0];
	//	if(δt > ival+Slop || δt < ival-Slop)
	//		print("alarm %d inaccurate %ld want %d %ld", n, δt, ival, δt-ival);
		if(δt > ival+Slop1 || δt < ival-Slop1){
			δ = δt-ival;
			print("alarm %d inaccurate %ld want %d %ld\n", n, δt, ival, δ);
			nmiss++;
			δ = abs(δ);
			if(δ > maxmiss)
				maxmiss = δ;
			missmsec += δ;
		}
	}
}

void
main(void)
{
	int i;
	Waitmsg *w;
	static int primes[] = {
		101, 103, 107, 109, 113, 127, 131, 137, 139, 149,
		151, 157, 163, 167, 173, 179, 181, 191, 193, 197,
		199, 211, 223, 227, 229, 233, 239, 241, 251, 257,
		263, 269, 271, 277, 281, 283, 293, 307, 311, 313,
		317, 331, 337, 347, 349, 353, 359, 367, 373, 379,
		383, 389, 397, 401, 409, 419, 421, 431, 433, 439,
		443, 449, 457, 461, 463, 467, 479, 487, 491, 499,
		503, 509, 521, 523, 541, 547, 557, 563, 569, 571,
		577, 587, 593, 599, 601, 607, 613, 617, 619, 631,
		641, 643, 647, 653, 659, 661, 673, 677, 683, 691,
	};

	for(i = 0; i < nelem(primes); i++)
		if(fork() == 0)
			alarmproc(primes[i]);
	while((w = wait()) != nil)
		free(w);
	exits("");
}