Messages in this thread | | | From | Vladimir Oltean <> | Subject | Re: [PATCH v2 net-next 7/7] net/sched: taprio: replace safety precautions with comments | Date | Wed, 21 Sep 2022 00:16:26 +0000 |
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On Tue, Sep 20, 2022 at 02:01:19PM -0700, Jakub Kicinski wrote: > On Thu, 15 Sep 2022 13:50:46 +0300 Vladimir Oltean wrote: > > 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. > > Another option is DEBUG_NET_WARN_ON_ONCE() FWIW, you probably know..
Just for replacing WARN_ON_ONCE(), yes, maybe, but when you factor in that the code also had calls to qdisc_drop(), I suppose you meant replacing it with something like this?
if (DEBUG_NET_WARN_ON_ONCE(unlikely(FULL_OFFLOAD_IS_ENABLED(q->flags)))) return qdisc_drop(skb, sch, to_free);
This won't work because DEBUG_NET_WARN_ON_ONCE() force-casts WARN_ON_ONCE() to void, discarding its evaluated value.
We'd be left with something custom like below:
if (IS_ENABLED(CONFIG_DEBUG_NET) && 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); }
which may work, but it's so odd looking that it's just not worth the trouble, I feel?
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