/* Acquire semaphore (subtract 1). */
static int
semacquire(Segment *s, long *addr, int block)
{
int acquired;
Sema phore;
if(canacquire(addr))
return 1;
if(!block)
return 0;
acquired = 0;
semqueue(s, addr, &phore);
for(;;){
phore.waiting = 1;
coherence();
if(canacquire(addr)){
acquired = 1;
break;
}
if(waserror())
break;
sleep(&phore, semawoke, &phore);
poperror();
}
semdequeue(s, &phore);
coherence(); /* not strictly necessary due to lock in semdequeue */
if(!phore.waiting)
semwakeup(s, addr, 1);
if(!acquired)
nexterror();
return 1;
}
/* Acquire semaphore or timeout */
static int
tsemacquire(Segment *s, long *addr, ulong ms)
{
int acquired;
Sema phore;
int timedout;
ulong t;
ulong tsemdbg;
if(canacquire(addr))
return 1;
if(ms == 0)
return 0;
acquired = 0;
timedout = 0;
semqueue(s, addr, &phore);
for(;;){
phore.waiting = 1;
coherence();
if(canacquire(addr)){
acquired = 1;
break;
}
if(waserror())
break;
t = m->ticks;
tsleep(&phore, semawoke, &phore, ms);
if((tsemdbg = TK2MS(m->ticks - t)) >= ms){
timedout = 1;
poperror();
break;
}
ms -= TK2MS(m->ticks - t);
poperror();
}
semdequeue(s, &phore);
coherence(); /* not strictly necessary due to lock in semdequeue */
if(!phore.waiting)
semwakeup(s, addr, 1);
if(timedout)
return 0;
if(!acquired)
nexterror();
return 1;
}