[PATCH v2 net-next 1/7] net/sched: taprio: taprio_offload_config_changed() is protected by rtnl_mutex

Vladimir Oltean
2022-09-15T10:51:11Z

The locking in taprio_offload_config_changed() is wrong (but also
inconsequentially so). The current_entry_lock does not serialize changes
to the admin and oper schedules, only to the current entry. In fact, the
rtnl_mutex does that, and that is taken at the time when taprio_change()
is called.

Replace the rcu_dereference_protected() method with the proper RCU
annotation, and drop the unnecessary spin lock.

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

net/sched/sch_taprio.c | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 5bffc37022e0..550afbbae8bc 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -1194,16 +1194,10 @@ static void taprio_offload_config_changed(struct taprio_sched *q)
{
struct sched_gate_list *oper, *admin;

- spin_lock(&q->current_entry_lock);
-
- oper = rcu_dereference_protected(q->oper_sched,
- lockdep_is_held(&q->current_entry_lock));
- admin = rcu_dereference_protected(q->admin_sched,
- lockdep_is_held(&q->current_entry_lock));
+ oper = rtnl_dereference(q->oper_sched);
+ admin = rtnl_dereference(q->admin_sched);

switch_schedules(q, &admin, &oper);
-
- spin_unlock(&q->current_entry_lock);
}

static u32 tc_map_to_queue_mask(struct net_device *dev, u32 tc_mask)
--
2.34.1