[dpdk-dev] [PATCH v2] event/dsw: avoid credit leak on oversized enqueue bursts

["Mattias Rönnblom" <mattias.ronnblom@ericsson.com>]

If an application issues rte_event_enqueue_new_burst() or
rte_event_enqueue_forward_burst() call with a burst of events longer
than the configured max enqueue burst size, DSW allocates credits not
only for events actually enqueued, but for the complete burst. If this
process is repeated, enough credits will have leaked to cause the
event device to backpressure (i.e. disallow) any new enqueue
operations.

In addition, the port-level enqueue xstats will log the wrong number
of events enqueued for oversized enqueues.

This patch makes DSW gracefully handle oversized enqueue bursts.

Fixes: 1c8e3caa3bfb ("event/dsw: add event scheduling and device start/stop")
Cc: stable@dpdk.org

Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
---
 drivers/event/dsw/dsw_event.c | 38 ++++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/drivers/event/dsw/dsw_event.c b/drivers/event/dsw/dsw_event.c
index 1641c2d06..eae53b240 100644
--- a/drivers/event/dsw/dsw_event.c
+++ b/drivers/event/dsw/dsw_event.c
@@ -1018,12 +1018,12 @@ dsw_event_enqueue(void *port, const struct rte_event *ev)
 }
 
 static __rte_always_inline uint16_t
-dsw_event_enqueue_burst_generic(void *port, const struct rte_event events[],
+dsw_event_enqueue_burst_generic(struct dsw_port *source_port,
+				const struct rte_event events[],
 				uint16_t events_len, bool op_types_known,
 				uint16_t num_new, uint16_t num_release,
 				uint16_t num_non_release)
 {
-	struct dsw_port *source_port = port;
 	struct dsw_evdev *dsw = source_port->dsw;
 	bool enough_credits;
 	uint16_t i;
@@ -1047,13 +1047,10 @@ dsw_event_enqueue_burst_generic(void *port, const struct rte_event events[],
 	 */
 	if (unlikely(events_len == 0)) {
 		dsw_port_note_op(source_port, DSW_MAX_PORT_OPS_PER_BG_TASK);
-		dsw_port_flush_out_buffers(dsw, port);
+		dsw_port_flush_out_buffers(dsw, source_port);
 		return 0;
 	}
 
-	if (unlikely(events_len > source_port->enqueue_depth))
-		events_len = source_port->enqueue_depth;
-
 	dsw_port_note_op(source_port, events_len);
 
 	if (!op_types_known)
@@ -1109,24 +1106,41 @@ uint16_t
 dsw_event_enqueue_burst(void *port, const struct rte_event events[],
 			uint16_t events_len)
 {
-	return dsw_event_enqueue_burst_generic(port, events, events_len, false,
-					       0, 0, 0);
+	struct dsw_port *source_port = port;
+
+	if (unlikely(events_len > source_port->enqueue_depth))
+		events_len = source_port->enqueue_depth;
+
+	return dsw_event_enqueue_burst_generic(source_port, events,
+					       events_len, false, 0, 0, 0);
 }
 
 uint16_t
 dsw_event_enqueue_new_burst(void *port, const struct rte_event events[],
 			    uint16_t events_len)
 {
-	return dsw_event_enqueue_burst_generic(port, events, events_len, true,
-					       events_len, 0, events_len);
+	struct dsw_port *source_port = port;
+
+	if (unlikely(events_len > source_port->enqueue_depth))
+		events_len = source_port->enqueue_depth;
+
+	return dsw_event_enqueue_burst_generic(source_port, events,
+					       events_len, true, events_len,
+					       0, events_len);
 }
 
 uint16_t
 dsw_event_enqueue_forward_burst(void *port, const struct rte_event events[],
 				uint16_t events_len)
 {
-	return dsw_event_enqueue_burst_generic(port, events, events_len, true,
-					       0, 0, events_len);
+	struct dsw_port *source_port = port;
+
+	if (unlikely(events_len > source_port->enqueue_depth))
+		events_len = source_port->enqueue_depth;
+
+	return dsw_event_enqueue_burst_generic(source_port, events,
+					       events_len, true, 0, 0,
+					       events_len);
 }
 
 uint16_t
-- 
2.17.1