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sgi: cleanup timer code

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- no need to splhi() in timerset, always called with
  interrupts off.

- make timerset always update the period (next == 0)

- remove period update in fastticks(), simplify
  delta calculation.
This commit is contained in:
cinap_lenrek 2017-01-22 20:39:14 +01:00
parent a2eafd2cb0
commit 6cb359cc00
1 changed files with 10 additions and 16 deletions
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26
sys/src/9/sgi/clock.c
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@ -83,7 +83,8 @@ clockinit(void)
m->maxperiod = Basetickfreq / HZ; m->maxperiod = Basetickfreq / HZ;
m->minperiod = Basetickfreq / (100*HZ); m->minperiod = Basetickfreq / (100*HZ);
wrcompare(rdcount()+m->maxperiod); m->lastcount = rdcount();
wrcompare(m->lastcount+m->maxperiod);
intron(INTR7); intron(INTR7);
} }
@ -128,12 +129,7 @@ fastticks(uvlong *hz)
/* avoid reentry on interrupt or trap, to prevent recursion */ /* avoid reentry on interrupt or trap, to prevent recursion */
x = splhi(); x = splhi();
count = rdcount(); count = rdcount();
if(rdcompare() - count > m->maxperiod) delta = count - m->lastcount;
wrcompare(count+m->maxperiod);
if (count < m->lastcount) /* wrapped around? */
delta = count + ((1ull<<32) - m->lastcount);
else
delta = count - m->lastcount;
m->lastcount = count; m->lastcount = count;
m->fastticks += delta; m->fastticks += delta;
splx(x); splx(x);
@ -150,18 +146,16 @@ perfticks(void)
void void
timerset(Tval next) timerset(Tval next)
{ {
int x;
long period; long period;
if(next == 0) if(next == 0)
return;
x = splhi(); /* don't let us get scheduled */
period = next - fastticks(nil);
if(period > m->maxperiod - m->minperiod)
period = m->maxperiod; period = m->maxperiod;
else if(period < m->minperiod) else {
period = m->minperiod; period = next - fastticks(nil);
if(period > m->maxperiod)
period = m->maxperiod;
else if(period < m->minperiod)
period = m->minperiod;
}
wrcompare(rdcount()+period); wrcompare(rdcount()+period);
splx(x);
} }