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Revert "MEDIUM: queue: unlock as soon as possible"

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This reverts commit 5b39275311.

The recent changes since 5304669e1 MEDIUM: queue: make
pendconn_process_next_strm() only return the pendconn opened a tiny race
condition between stream_free() and process_srv_queue(), as the pendconn
is accessed outside of the lock, possibly while it's being freed. A
different approach is required.
This commit is contained in:
Willy Tarreau 2021-06-24 07:21:59 +02:00
parent 2bf3f2cf7f
commit 90a160a465
1 changed files with 10 additions and 15 deletions
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25
src/queue.c
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@ -270,23 +270,20 @@ static struct pendconn *pendconn_process_next_strm(struct server *srv, struct pr
u32 pkey, ppkey;
p = NULL;
if (srv->queue.length) {
HA_SPIN_LOCK(QUEUE_LOCK, &srv->queue.lock);
HA_SPIN_LOCK(QUEUE_LOCK, &srv->queue.lock);
if (srv->queue.length)
p = pendconn_first(&srv->queue.head);
if (!p)
HA_SPIN_UNLOCK(QUEUE_LOCK, &srv->queue.lock);
}
pp = NULL;
if (px_ok && px->queue.length) {
HA_SPIN_LOCK(QUEUE_LOCK, &px->queue.lock);
HA_SPIN_LOCK(QUEUE_LOCK, &px->queue.lock);
if (px_ok && px->queue.length)
pp = pendconn_first(&px->queue.head);
if (!pp)
HA_SPIN_UNLOCK(QUEUE_LOCK, &px->queue.lock);
}
if (!p && !pp)
if (!p && !pp) {
HA_SPIN_UNLOCK(QUEUE_LOCK, &px->queue.lock);
HA_SPIN_UNLOCK(QUEUE_LOCK, &srv->queue.lock);
return NULL;
}
else if (!pp)
goto use_p; /* p != NULL */
else if (!p)
@ -314,18 +311,16 @@ static struct pendconn *pendconn_process_next_strm(struct server *srv, struct pr
use_pp:
/* Let's switch from the server pendconn to the proxy pendconn */
if (p)
HA_SPIN_UNLOCK(QUEUE_LOCK, &srv->queue.lock);
__pendconn_unlink_prx(pp);
HA_SPIN_UNLOCK(QUEUE_LOCK, &px->queue.lock);
HA_SPIN_UNLOCK(QUEUE_LOCK, &srv->queue.lock);
_HA_ATOMIC_INC(&px->queue.idx);
_HA_ATOMIC_DEC(&px->queue.length);
_HA_ATOMIC_DEC(&px->totpend);
p = pp;
goto unlinked;
use_p:
if (pp)
HA_SPIN_UNLOCK(QUEUE_LOCK, &px->queue.lock);
HA_SPIN_UNLOCK(QUEUE_LOCK, &px->queue.lock);
__pendconn_unlink_srv(p);
HA_SPIN_UNLOCK(QUEUE_LOCK, &srv->queue.lock);
_HA_ATOMIC_INC(&srv->queue.idx);