On 28/04/16 18:08, Bala Manoharan wrote:
On 28 April 2016 at 21:50, Zoltan Kiss <zoltan.k...@linaro.org
<mailto:zoltan.k...@linaro.org>> wrote:
On 28/04/16 10:29, Bala Manoharan wrote:
On 27 April 2016 at 21:43, Zoltan Kiss <zoltan.k...@linaro.org
<mailto:zoltan.k...@linaro.org>
<mailto:zoltan.k...@linaro.org <mailto:zoltan.k...@linaro.org>>>
wrote:
Move release to _odp_packet_classifier(), because caller
has no way to
know if new_pkt were allocated. In that case there would be
a double
free
on pkt, and new_pkt would be leaked.
I am little skeptical about this classifier module freeing up
the packet
since the error in CoS can only happen during a wrong
configuration by
the application
I'm not sure this is wrong config:
- cos == NULL shouldn't happen, my understanding is that not setting
a default queue is impossible (although I haven't found it spelled
out in the header files explicitly), so this is an internal error
Whenever application creates a pktio with enable_classifier field set in
odp_pktio_params_t then it should call the function
odp_pktio_default_cos_set() to set the default CoS with the pktio. The
scenario of cos == NULL will only occur if a pktio is created with
classification enabled and default CoS not set and hence this is a
configuration error.
So you say in this case these packets should end up on
entry->s.in_queue[index[idx]].queue in pktin_poll()? Why? Or do you have
something else in mind?
I would say it's better if different pktio's handle this the same way.
- (cos->s.queue == NULL || cos->s.pool == NULL) means the packet
should be dropped. Although I don't know how drop_policy should
affect this, it's not clear from the description of odp_cls_cos_create()
- (entry == NULL) is impossible at the moment, but as you said, in
the future other callers might make this mistake, so better to be
prepared.
- odp_packet_copy() fails means we can't put this packet where it
supposed to arrive, I think it would be very confusing for the
application to receive it then
- queue_enq() failure is again a sign of serious issues
pool or queue error could also be transient the pool could get empty
This is not an overload issue, as odp_cls_cos_create() says:
"@note ODP_QUEUE_INVALID and ODP_POOL_INVALID are valid values for queue
and pool associated with a class of service and when any one of these
values are configured as INVALID then the packets assigned to the CoS
gets dropped."
after sometime depending upon the load in the network. Imagine a
scenario where the application sends a decrypted packet into the
loopback device for classification and would not want the packet to be
dropped immediately on transient pool exhaustion but would prefer
delayed sending of the packet.
Or do you mean when odp_packet_copy() fails? (This second part suggest
that) Still, how would that happen? Currently this call graph looks like
this:
schedule()
pktin_poll() [currently it can place returned packets on
entry->s.in_queue[index[idx]].queue]
odp_pktin_recv()
[pktio's receive function]
[_odp_packet_classifier() or _odp_packet_cls_enq(), depending on your pktio]
At which level should we handle this and how?
(And I think we still should drop the packets in the other error cases
I've mentioned, in an unified way for all pktios)
and hence it would be better if the error is percolated
to the application
The error itself is returned through odp_pktin_recv() when you apply
the next two patch, but as we discussed if classification is enabled
it shouldn't be called directly. pktin_poll() will notice that
though, and print a message, but it won't enqueue when queue_enq()
fails, see the 3rd patch.
so that he can take some intelligent action ( either
reconfigure classification and send the packet again or free the
packet ).
This function is only used on the receive side, I'm not sure what
you mean by "send the packet again".
The application might want some specific packets not be dropped under
any scenario even when there is a rate limiting and in case of loopback
mode the classifier module is attached directly to the output as if
there is a physical loopback and hence in that scenario the loopback
device might want to send the packet again after sometime when the pool
or queue gets empty rather than dropping it immediately.
So you say the loopback receive function should get back the packets
when odp_packet_copy() fails, and send it again to loopback?
That's a hard question whether its a good idea or not. You can count on
the fact that the packets are never lost there, but you are risking
recovery time during an overload scenario (or maybe even a deadlock, if
nothing else releases buffer from the pool, you'll keep enqueuing the
same packets)
Regarding the issue of freeing up the packet when a new packet is
created by the classification module, we can better change the
signature
of _odp_packet_classifier() API to receive odp_packet_t as a
pointer and
update the pointer with new packet.
The main reason I am against freeing up the packet inside
classification
module is that this function is currently called only by
loopback device
but in future development it could be called from other sources
also and
hence it is better if freeing of the packet during error is done
by the
caller rather than classification module.
I think we should implement this when we get there, and see it fit
better. Currently it's broken anyway.
Plus, why would it be better to release by the caller, rather than
on the spot? As I explained above, these error cases seems to be
major internal issues, none of them seem like the caller can do
anything.
Why don't we implement it now rather than change it in the future?
The caller in this case is also internal functions (eg socket, loopback)
as _odp_packet_classifier() is an internal function and cannot be
directly called by the application, so the idea here is whether the
packets are freed up by _odp_packet_classifier() internal function or
its caller the socket function both of which are internal functions in
the linux-generic. I prefer the latter so that any future devices could
be handled gracefully.
I think it's better if all pktio's handle these errors in the same way,
and by default it is by dropping packets. It's easier to enforce if we
handle that in _odp_packet_classifier() and _odp_packet_cls_enq().
The only scenario when I can imagine to pass back the packet is when
odp_packet_copy() fails, but even then re-sending might not be a good
idea, as I explained above.
Most importantly the point we both are discussing is very narrow and
code changes are minimal, If you feel strongly then you can go ahead and
implement your way now and we can make any change in the future. I don't
want to drag this discussion and delay this patch any longer.
Regards,
Bala
Regards,
Bala
Signed-off-by: Zoltan Kiss <zoltan.k...@linaro.org
<mailto:zoltan.k...@linaro.org>
<mailto:zoltan.k...@linaro.org
<mailto:zoltan.k...@linaro.org>>>
---
platform/linux-generic/odp_classification.c | 21
++++++++++++---------
platform/linux-generic/pktio/loop.c | 1 -
2 files changed, 12 insertions(+), 10 deletions(-)
diff --git a/platform/linux-generic/odp_classification.c
b/platform/linux-generic/odp_classification.c
index 3a18a78..a1466fd 100644
--- a/platform/linux-generic/odp_classification.c
+++ b/platform/linux-generic/odp_classification.c
@@ -734,22 +734,20 @@ int _odp_packet_classifier(pktio_entry_t
*entry, odp_packet_t pkt)
odp_packet_t new_pkt;
uint8_t *pkt_addr;
- if (entry == NULL)
+ if (entry == NULL) {
+ odp_packet_free(pkt);
return -1;
+ }
pkt_hdr = odp_packet_hdr(pkt);
pkt_addr = odp_packet_data(pkt);
/* Matching PMR and selecting the CoS for the packet*/
cos = pktio_select_cos(entry, pkt_addr, pkt_hdr);
- if (cos == NULL)
- return -1;
-
- if (cos->s.pool == NULL)
- return -1;
-
- if (cos->s.queue == NULL)
+ if (cos == NULL || cos->s.queue == NULL ||
cos->s.pool ==
NULL) {
+ odp_packet_free(pkt);
return -1;
+ }
if (odp_packet_pool(pkt) != cos->s.pool->s.pool_hdl) {
new_pkt = odp_packet_copy(pkt,
cos->s.pool->s.pool_hdl);
@@ -762,7 +760,12 @@ int _odp_packet_classifier(pktio_entry_t
*entry, odp_packet_t pkt)
/* Enqueuing the Packet based on the CoS */
queue = cos->s.queue;
- return queue_enq(queue,
odp_buf_to_hdr((odp_buffer_t)new_pkt), 0);
+ if (queue_enq(queue,
odp_buf_to_hdr((odp_buffer_t)new_pkt),
0)) {
+ odp_packet_free(new_pkt);
+ return -1;
+ } else {
+ return 0;
+ }
}
cos_t *pktio_select_cos(pktio_entry_t *entry, const
uint8_t *pkt_addr,
diff --git a/platform/linux-generic/pktio/loop.c
b/platform/linux-generic/pktio/loop.c
index f6a8c1d..676e98b 100644
--- a/platform/linux-generic/pktio/loop.c
+++ b/platform/linux-generic/pktio/loop.c
@@ -76,7 +76,6 @@ static int loopback_recv(pktio_entry_t
*pktio_entry, odp_packet_t pkts[],
} else {
pktio_entry->s.stats.in_errors +=
odp_packet_len(pkt);
- odp_packet_free(pkt);
}
}
nbr = j;
--
1.9.1
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