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kernel: always do unsigned subtractions for m->ticks delta for updatecpu() and rebalance(), handle ticks wrap arround in hzsched()

--- a/sys/src/9/port/proc.c

+++ b/sys/src/9/port/proc.c

@@ -201,7 +201,7 @@

 	/* unless preempted, get to run for at least 100ms */

 	if(anyhigher()

-	|| (!up->fixedpri && m->ticks > m->schedticks && anyready())){

+	|| (!up->fixedpri && (long)(m->ticks - m->schedticks) > 0 && anyready())){

 		m->readied = nil;	/* avoid cooperative scheduling */

 		up->delaysched++;

 	}

@@ -271,8 +271,7 @@

 void

 updatecpu(Proc *p)

 {

-	int n, t, ocpu;

-	int D = schedgain*HZ*Scaling;

+	ulong t, ocpu, n, D;

 	if(p->edf != nil)

 		return;

@@ -279,10 +278,11 @@

 	t = MACHP(0)->ticks*Scaling + Scaling/2;

 	n = t - p->lastupdate;

-	p->lastupdate = t;

-

 	if(n == 0)

 		return;

+	p->lastupdate = t;

+

+	D = schedgain*HZ*Scaling;

 	if(n > D)

 		n = D;

@@ -294,8 +294,7 @@

 		t = (t*(D-n))/D;

 		p->cpu = 1000 - t;

 	}

-

-//iprint("pid %d %s for %d cpu %d -> %d\n", p->pid,p==up?"active":"inactive",n, ocpu,p->cpu);

+//iprint("pid %lud %s for %lud cpu %lud -> %lud\n", p->pid,p==up?"active":"inactive",n, ocpu,p->cpu);

 }

 /*

@@ -463,9 +462,10 @@

 static void

 rebalance(void)

 {

-	int pri, npri, t, x;

+	int pri, npri, x;

 	Schedq *rq;

 	Proc *p;

+	ulong t;

 	t = m->ticks;

 	if(t - balancetime < HZ)