*Hi Damjan*
*Thnaks for your answer,*
*I think it is possible (I encountered this problem) to have deadlock even when
I use separate CPU for handoff and NAT processing, Or same CPU with congestion
drop mechanism.*
*I studied the code and separate the CPUs of handoff and NAT processing, in
this situation I think just in one case deadlock for handoff may be happen*
*suppose if worker A wants to dequeue but elt->valid value is zero so
vlib_frame_queue_dequeue function return and do not dequeue, as result fq->head
will never increase:*
int vlib_frame_queue_dequeue (vlib_main_t *vm, vlib_frame_queue_main_t *fqm)
{
....
while (1)
{
if (fq->head == fq->tail)
return processed;
elt = fq->elts + ((fq->head + 1) & (fq->nelts - 1));
*if (!elt->valid)*
{
fq->head_hint = fq->head;
return processed;
}
....
}
*and on the other side , worker B ( on handoff node) wants to enqueue but ring
is full so wait :*
static inline vlib_frame_queue_elt_t *
vlib_get_frame_queue_elt (u32 frame_queue_index, u32 index)
{
...
new_tail = __sync_add_and_fetch (&fq->tail, 1);
/* Wait until a ring slot is available */
while (new_tail >= fq->head_hint + fq->nelts)
vlib_worker_thread_barrier_check ();
....
}
*therefore worker B never exit from while loop* , *do you think it is possible
?*
-=-=-=-=-=-=-=-=-=-=-=-
Links: You receive all messages sent to this group.
View/Reply Online (#11803): https://lists.fd.io/g/vpp-dev/message/11803
Mute This Topic: https://lists.fd.io/mt/28878687/21656
Group Owner: vpp-dev+ow...@lists.fd.io
Unsubscribe: https://lists.fd.io/g/vpp-dev/unsub [arch...@mail-archive.com]
-=-=-=-=-=-=-=-=-=-=-=-
