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Revert "MEDIUM: queue: move the queue lock manipulation to pendconn_process_next_strm()"

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This reverts commit 9a6d0ddbd6788a05c6730bf0e9e8550d7c5b11aa.

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 07:22:03 +02:00
parent 90a160a465
commit 5343d8ed6f
1 changed files with 9 additions and 12 deletions
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21
src/queue.c
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@ -255,8 +255,8 @@ static struct pendconn *pendconn_first(struct eb_root *pendconns)
*
* The proxy's queue will be consulted only if px_ok is non-zero.
*
* This function uses both the proxy and the server queues' lock. Today it is
* only called by process_srv_queue.
* This function must only be called if the server queue _AND_ the proxy queue
* are locked (if pk_ok is set). Today it is only called by process_srv_queue.
*
* The function returns the dequeued pendconn on success or NULL if none is
* available. It's up to the caller to add the corresponding stream to the
@ -270,20 +270,15 @@ static struct pendconn *pendconn_process_next_strm(struct server *srv, struct pr
u32 pkey, ppkey;
p = NULL;
HA_SPIN_LOCK(QUEUE_LOCK, &srv->queue.lock);
if (srv->queue.length)
p = pendconn_first(&srv->queue.head);
pp = NULL;
HA_SPIN_LOCK(QUEUE_LOCK, &px->queue.lock);
if (px_ok && px->queue.length)
pp = pendconn_first(&px->queue.head);
if (!p && !pp) {
HA_SPIN_UNLOCK(QUEUE_LOCK, &px->queue.lock);
HA_SPIN_UNLOCK(QUEUE_LOCK, &srv->queue.lock);
if (!p && !pp)
return NULL;
}
else if (!pp)
goto use_p; /* p != NULL */
else if (!p)
@ -312,17 +307,13 @@ 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 */
__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:
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);
_HA_ATOMIC_DEC(&srv->queue.length);
_HA_ATOMIC_DEC(&px->totpend);
@ -356,8 +347,14 @@ void process_srv_queue(struct server *s)
while (s->served < maxconn) {
struct pendconn *pc;
HA_SPIN_LOCK(QUEUE_LOCK, &s->queue.lock);
HA_SPIN_LOCK(QUEUE_LOCK, &p->queue.lock);
pc = pendconn_process_next_strm(s, p, px_ok);
HA_SPIN_UNLOCK(QUEUE_LOCK, &p->queue.lock);
HA_SPIN_UNLOCK(QUEUE_LOCK, &s->queue.lock);
if (!pc)
break;