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Rewrite to remove dependence on rendezvous and its bizarre

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data structures.  Makes it easier to use pthreads too.
Still need to add code for non-pthreads systems.

Just a checkpoint to switch work to another machine.
This commit is contained in:
rsc 2004-09-17 00:38:29 +00:00
parent 984e353160
commit 06bb4ed20d
15 changed files with 205 additions and 218 deletions
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43
src/libthread/channel.c
View file

@ -2,7 +2,7 @@
static Lock chanlock; /* central channel access lock */
static void enqueue(Alt*, Channel**);
static void enqueue(Alt*, Thread*);
static void dequeue(Alt*);
static int altexec(Alt*, int);
@ -29,7 +29,7 @@ canexec(Alt *a)
/* are there senders or receivers blocked? */
otherop = (CHANSND+CHANRCV) - a->op;
for(i=0; i<c->nentry; i++)
if(c->qentry[i] && c->qentry[i]->op==otherop && *c->qentry[i]->tag==nil){
if(c->qentry[i] && c->qentry[i]->op==otherop && c->qentry[i]->thread==nil){
_threaddebug(DBGCHAN, "can rendez alt %p chan %p", a, c);
return 1;
}
@ -100,9 +100,8 @@ static int
_alt(Alt *alts)
{
Alt *a, *xa;
Channel *volatile c;
Channel *c;
int n, s;
ulong r;
Thread *t;
/*
@ -131,7 +130,7 @@ _alt(Alt *alts)
xa->entryno = -1;
if(xa->op == CHANNOP)
continue;
c = xa->c;
if(c==nil){
unlock(&chanlock);
@ -153,11 +152,11 @@ _threadnalt++;
}
/* enqueue on all channels. */
c = nil;
t->altc = nil;
for(xa=alts; xa->op!=CHANEND; xa++){
if(xa->op==CHANNOP)
continue;
enqueue(xa, (Channel**)&c);
enqueue(xa, t);
}
/*
@ -166,25 +165,20 @@ _threadnalt++;
* is interrupted -- someone else might come
* along and try to rendezvous with us, so
* we need to be here.
*
* actually, now we're assuming no interrupts.
*/
Again:
/*Again:*/
t->alt = alts;
t->chan = Chanalt;
unlock(&chanlock);
t->altrend.l = &chanlock;
_procsplx(s);
r = _threadrendezvous((ulong)&c, 0);
_threadsleep(&t->altrend);
s = _procsplhi();
lock(&chanlock);
if(r==~0){ /* interrupted */
if(c!=nil) /* someone will meet us; go back */
goto Again;
c = (Channel*)~0; /* so no one tries to meet us */
}
/* dequeue from channels, find selected one */
a = nil;
c = t->altc;
for(xa=alts; xa->op!=CHANEND; xa++){
if(xa->op==CHANNOP)
continue;
@ -385,12 +379,12 @@ if(c->nentry > _threadhighnentry) _threadhighnentry = c->nentry;
}
static void
enqueue(Alt *a, Channel **c)
enqueue(Alt *a, Thread *t)
{
int i;
_threaddebug(DBGCHAN, "Queueing alt %p on channel %p", a, a->c);
a->tag = c;
a->thread = t;
i = emptyentry(a->c);
a->c->qentry[i] = a;
}
@ -466,7 +460,7 @@ altexec(Alt *a, int spl)
b = nil;
me = a->v;
for(i=0; i<c->nentry; i++)
if(c->qentry[i] && c->qentry[i]->op==otherop && *c->qentry[i]->tag==nil)
if(c->qentry[i] && c->qentry[i]->op==otherop && c->qentry[i]->thread==nil)
if(nrand(++n) == 0)
b = c->qentry[i];
if(b != nil){
@ -493,13 +487,12 @@ altexec(Alt *a, int spl)
else
altcopy(waiter, me, c->e);
}
*b->tag = c; /* commits us to rendezvous */
b->thread->altc = c;
_procwakeup(&b->thread->altrend);
_threaddebug(DBGCHAN, "chanlock is %lud", *(ulong*)(void*)&chanlock);
_threaddebug(DBGCHAN, "unlocking the chanlock");
unlock(&chanlock);
_procsplx(spl);
_threaddebug(DBGCHAN, "chanlock is %lud", *(ulong*)(void*)&chanlock);
while(_threadrendezvous((ulong)b->tag, 0) == ~0)
;
return 1;
}