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net/sched: taprio: make q->picos_per_byte available to fill_sched_entry()

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In commit b5b73b26b3 ("taprio: Fix allowing too small intervals"), a
comparison of user input against length_to_duration(q, ETH_ZLEN) was
introduced, to avoid RCU stalls due to frequent hrtimers.

The implementation of length_to_duration() depends on q->picos_per_byte
being set for the link speed. The blamed commit in the Fixes: tag has
moved this too late, so the checks introduced above are ineffective.
The q->picos_per_byte is zero at parse_taprio_schedule() ->
parse_sched_list() -> parse_sched_entry() -> fill_sched_entry() time.

Move the taprio_set_picos_per_byte() call as one of the first things in
taprio_change(), before the bulk of the netlink attribute parsing is
done. That's because it is needed there.

Add a selftest to make sure the issue doesn't get reintroduced.

Fixes: 09dbdf28f9 ("net/sched: taprio: fix calculation of maximum gate durations")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20240527153955.553333-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Vladimir Oltean 2024-05-27 18:39:54 +03:00 committed by Jakub Kicinski
parent 56a5cf538c
commit e634134180
2 changed files with 25 additions and 1 deletions
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4
net/sched/sch_taprio.c
View File

@ -1848,6 +1848,9 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
}
q->flags = taprio_flags;
/* Needed for length_to_duration() during netlink attribute parsing */
taprio_set_picos_per_byte(dev, q);
err = taprio_parse_mqprio_opt(dev, mqprio, extack, q->flags);
if (err < 0)
return err;
@ -1907,7 +1910,6 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
if (err < 0)
goto free_sched;
taprio_set_picos_per_byte(dev, q);
taprio_update_queue_max_sdu(q, new_admin, stab);
if (FULL_OFFLOAD_IS_ENABLED(q->flags))

22
tools/testing/selftests/tc-testing/tc-tests/qdiscs/taprio.json
View File

@ -132,6 +132,28 @@
"echo \"1\" > /sys/bus/netdevsim/del_device"
]
},
{
"id": "6f62",
"name": "Add taprio Qdisc with too short interval",
"category": [
"qdisc",
"taprio"
],
"plugins": {
"requires": "nsPlugin"
},
"setup": [
"echo \"1 1 8\" > /sys/bus/netdevsim/new_device"
],
"cmdUnderTest": "$TC qdisc add dev $ETH root handle 1: taprio num_tc 2 queues 1@0 1@1 sched-entry S 01 300 sched-entry S 02 1700 clockid CLOCK_TAI",
"expExitCode": "2",
"verifyCmd": "$TC qdisc show dev $ETH",
"matchPattern": "qdisc taprio 1: root refcnt",
"matchCount": "0",
"teardown": [
"echo \"1\" > /sys/bus/netdevsim/del_device"
]
},
{
"id": "3e1e",
"name": "Add taprio Qdisc with an invalid cycle-time",