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kernel: tsemacquire() use MACHP(0)->ticks for time delta

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we might wake up on a different cpu after the sleep so
delta from machX->ticks - machY->ticks can become negative
giving spurious timeouts. to avoid this always use the
same mach 0 tick counter for the delta.
This commit is contained in:
cinap_lenrek 2016-09-07 23:36:04 +02:00
parent bfd8098b8d
commit 1848f4e946
1 changed files with 5 additions and 5 deletions
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10
sys/src/9/port/sysproc.c
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@ -1126,7 +1126,7 @@ static int
tsemacquire(Segment *s, long *addr, ulong ms)
{
int acquired, timedout;
ulong t, elms;
ulong t;
Sema phore;
if(canacquire(addr))
@ -1144,15 +1144,15 @@ tsemacquire(Segment *s, long *addr, ulong ms)
}
if(waserror())
break;
t = m->ticks;
t = MACHP(0)->ticks;
tsleep(&phore, semawoke, &phore, ms);
elms = TK2MS(m->ticks - t);
t = TK2MS(MACHP(0)->ticks - t);
poperror();
if(elms >= ms){
if(t >= ms){
timedout = 1;
break;
}
ms -= elms;
ms -= t;
}
semdequeue(s, &phore);
coherence(); /* not strictly necessary due to lock in semdequeue */