[PATCH v2 net-next 7/7] net/sched: taprio: replace safety precautions with comments

Vladimir Oltean
2022-09-15T10:52:13Z

The WARN_ON_ONCE() checks introduced in commit 13511704f8d7 ("net:
taprio offload: enforce qdisc to netdev queue mapping") take a small
toll on performance, but otherwise, the conditions are never expected to
happen. Replace them with comments, such that the information is still
conveyed to developers.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
v1->v2: patch is new

net/sched/sch_taprio.c | 24 +++++++++---------------
1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index bc93f709d354..8ae454052201 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -433,6 +433,9 @@ static int taprio_enqueue_one(struct sk_buff *skb, struct Qdisc *sch,
return qdisc_enqueue(skb, child, to_free);
}

+/* Will not be called in the full offload case, since the TX queues are
+ * attached to the Qdisc created using qdisc_create_dflt()
+ */
static int taprio_enqueue(struct sk_buff *skb, struct Qdisc *sch,
struct sk_buff **to_free)
{
@@ -440,11 +443,6 @@ static int taprio_enqueue(struct sk_buff *skb, struct Qdisc *sch,
struct Qdisc *child;
int queue;

- if (unlikely(FULL_OFFLOAD_IS_ENABLED(q->flags))) {
- WARN_ONCE(1, "Trying to enqueue skb into the root of a taprio qdisc configured with full offload\n");
- return qdisc_drop(skb, sch, to_free);
- }
-
queue = skb_get_queue_mapping(skb);

child = q->qdiscs[queue];
@@ -490,6 +488,9 @@ static int taprio_enqueue(struct sk_buff *skb, struct Qdisc *sch,
return taprio_enqueue_one(skb, sch, child, to_free);
}

+/* Will not be called in the full offload case, since the TX queues are
+ * attached to the Qdisc created using qdisc_create_dflt()
+ */
static struct sk_buff *taprio_peek(struct Qdisc *sch)
{
struct taprio_sched *q = qdisc_priv(sch);
@@ -499,11 +500,6 @@ static struct sk_buff *taprio_peek(struct Qdisc *sch)
u32 gate_mask;
int i;

- if (unlikely(FULL_OFFLOAD_IS_ENABLED(q->flags))) {
- WARN_ONCE(1, "Trying to peek into the root of a taprio qdisc configured with full offload\n");
- return NULL;
- }
-
rcu_read_lock();
entry = rcu_dereference(q->current_entry);
gate_mask = entry ? entry->gate_mask : TAPRIO_ALL_GATES_OPEN;
@@ -546,6 +542,9 @@ static void taprio_set_budget(struct taprio_sched *q, struct sched_entry *entry)
atomic64_read(&q->picos_per_byte)));
}

+/* Will not be called in the full offload case, since the TX queues are
+ * attached to the Qdisc created using qdisc_create_dflt()
+ */
static struct sk_buff *taprio_dequeue(struct Qdisc *sch)
{
struct taprio_sched *q = qdisc_priv(sch);
@@ -555,11 +554,6 @@ static struct sk_buff *taprio_dequeue(struct Qdisc *sch)
u32 gate_mask;
int i;

- if (unlikely(FULL_OFFLOAD_IS_ENABLED(q->flags))) {
- WARN_ONCE(1, "Trying to dequeue from the root of a taprio qdisc configured with full offload\n");
- return NULL;
- }
-
rcu_read_lock();
entry = rcu_dereference(q->current_entry);
/* if there's no entry, it means that the schedule didn't
--
2.34.1