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kernel: stop queue bloat before allocating blocks

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This commit is contained in:
cinap_lenrek 2014-04-29 21:15:09 +02:00
parent a2f0fdbfa0
commit b7d8431036
1 changed files with 46 additions and 38 deletions
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84
sys/src/9/port/qio.c
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@ -1152,6 +1152,31 @@ qnotfull(void *a)
return q->len < q->limit || (q->state & Qclosed);
}
/*
* flow control, wait for queue to get below the limit
*/
static void
qflow(Queue *q)
{
for(;;){
if(q->noblock || qnotfull(q))
break;
ilock(q);
q->state |= Qflow;
iunlock(q);
eqlock(&q->wlock);
if(waserror()){
qunlock(&q->wlock);
nexterror();
}
sleep(&q->wr, qnotfull, q);
qunlock(&q->wlock);
poperror();
}
}
/*
* add a block to a queue obeying flow control
*/
@ -1182,17 +1207,11 @@ qbwrite(Queue *q, Block *b)
}
/* don't queue over the limit */
if(q->len >= q->limit){
if(q->noblock){
iunlock(q);
freeb(b);
poperror();
return n;
}
if(q->len >= q->limit*10){
iunlock(q);
error(Egreg);
}
if(q->len >= q->limit && q->noblock){
iunlock(q);
freeb(b);
poperror();
return n;
}
/* queue the block */
@ -1228,34 +1247,13 @@ qbwrite(Queue *q, Block *b)
}
/*
* flow control, wait for queue to get below the limit
* before allowing the process to continue and queue
* more. We do this here so that postnote can only
* interrupt us after the data has been queued. This
* means that things like 9p flushes and ssl messages
* will not be disrupted by software interrupts.
*
* Note - this is moderately dangerous since a process
* that keeps getting interrupted and rewriting will
* queue up to 10 times the queue limit before failing.
* flow control, before allowing the process to continue and
* queue more. We do this here so that postnote can only
* interrupt us after the data has been queued. This means that
* things like 9p flushes and ssl messages will not be disrupted
* by software interrupts.
*/
for(;;){
if(q->noblock || qnotfull(q))
break;
ilock(q);
q->state |= Qflow;
iunlock(q);
eqlock(&q->wlock);
if(waserror()){
qunlock(&q->wlock);
nexterror();
}
sleep(&q->wr, qnotfull, q);
qunlock(&q->wlock);
poperror();
}
qflow(q);
return n;
}
@ -1273,6 +1271,16 @@ qwrite(Queue *q, void *vp, int len)
QDEBUG if(!islo())
print("qwrite hi %#p\n", getcallerpc(&q));
/* stop queue bloat before allocating blocks */
if(q->len/2 >= q->limit && q->noblock == 0 && q->bypass == nil){
while(waserror()){
if(up->procctl == Proc_exitme || up->procctl == Proc_exitbig)
error(Egreg);
}
qflow(q);
poperror();
}
sofar = 0;
do {
n = len-sofar;