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net/sched: mq_prio: no longer acquire qdisc spinlocks in mqprio_dump_class_stats()

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Prepare mqprio_dump_class_stats() for RTNL avoidance.

Use RCU instead of RTNL, and no longer acquire each children spinlock.

As a bonus we no longer have to release/acquire d->lock.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Link: https://patch.msgid.link/20260510091455.4039245-9-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2026-05-10 09:14:55 +00:00 committed by Jakub Kicinski
parent bb19ce4c43
commit 881f7c5eff
1 changed files with 15 additions and 25 deletions
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40
net/sched/sch_mqprio.c
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@ -672,9 +672,11 @@ static int mqprio_dump_class(struct Qdisc *sch, unsigned long cl,
static int mqprio_dump_class_stats(struct Qdisc *sch, unsigned long cl,
struct gnet_dump *d)
__releases(d->lock)
__acquires(d->lock)
{
const struct Qdisc *qdisc;
int res = 0;
rcu_read_lock();
if (cl >= TC_H_MIN_PRIORITY) {
struct net_device *dev = qdisc_dev(sch);
struct netdev_tc_txq tc = dev->tc_to_txq[cl & TC_BITMASK];
@ -684,46 +686,34 @@ static int mqprio_dump_class_stats(struct Qdisc *sch, unsigned long cl,
int i;
gnet_stats_basic_sync_init(&bstats);
/* Drop lock here it will be reclaimed before touching
* statistics this is required because the d->lock we
* hold here is the look on dev_queue->qdisc_sleeping
* also acquired below.
*/
if (d->lock)
spin_unlock_bh(d->lock);
for (i = tc.offset; i < tc.offset + tc.count; i++) {
struct netdev_queue *q = netdev_get_tx_queue(dev, i);
struct Qdisc *qdisc = rtnl_dereference(q->qdisc);
spin_lock_bh(qdisc_lock(qdisc));
qdisc = rcu_dereference(q->qdisc);
gnet_stats_add_basic(&bstats, qdisc->cpu_bstats,
&qdisc->bstats, false);
&qdisc->bstats, true);
gnet_stats_add_queue(&qstats, qdisc->cpu_qstats,
&qdisc->qstats);
qlen += qdisc_qlen_lockless(qdisc);
spin_unlock_bh(qdisc_lock(qdisc));
}
qlen = qlen + qstats.qlen;
/* Reclaim root sleeping lock before completing stats */
if (d->lock)
spin_lock_bh(d->lock);
if (gnet_stats_copy_basic(d, NULL, &bstats, false) < 0 ||
gnet_stats_copy_queue(d, NULL, &qstats, qlen) < 0)
return -1;
res = -1;
} else {
struct netdev_queue *dev_queue = mqprio_queue_get(sch, cl);
sch = rtnl_dereference(dev_queue->qdisc_sleeping);
if (gnet_stats_copy_basic(d, sch->cpu_bstats,
&sch->bstats, true) < 0 ||
qdisc_qstats_copy(d, sch) < 0)
return -1;
qdisc = rcu_dereference(dev_queue->qdisc_sleeping);
if (gnet_stats_copy_basic(d, qdisc->cpu_bstats,
&qdisc->bstats, true) < 0 ||
qdisc_qstats_copy(d, qdisc) < 0)
res = -1;
}
return 0;
rcu_read_unlock();
return res;
}
static void mqprio_walk(struct Qdisc *sch, struct qdisc_walker *arg)