sched: sch_api: add missing rcu read lock to silence the warning
In case the qdisc_match_from_root function() is called from non-rcu path
with rtnl mutex held, a suspiciout rcu usage warning appears:
[ 241.504354] =============================
[ 241.504358] WARNING: suspicious RCU usage
[ 241.504366] 5.8.0-rc4-custom-01521-g72a7c7d549c3 #32 Not tainted
[ 241.504370] -----------------------------
[ 241.504378] net/sched/sch_api.c:270 RCU-list traversed in non-reader section!!
[ 241.504382]
other info that might help us debug this:
[ 241.504388]
rcu_scheduler_active = 2, debug_locks = 1
[ 241.504394] 1 lock held by tc/1391:
[ 241.504398] #0: ffffffff85a27850 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x49a/0xbd0
[ 241.504431]
stack backtrace:
[ 241.504440] CPU: 0 PID: 1391 Comm: tc Not tainted 5.8.0-rc4-custom-01521-g72a7c7d549c3 #32
[ 241.504446] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-2.fc32 04/01/2014
[ 241.504453] Call Trace:
[ 241.504465] dump_stack+0x100/0x184
[ 241.504482] lockdep_rcu_suspicious+0x153/0x15d
[ 241.504499] qdisc_match_from_root+0x293/0x350
Fix this by passing the rtnl held lockdep condition down to
hlist_for_each_entry_rcu()
Reported-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 11ebba6..2a76a2f 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -267,7 +267,8 @@ static struct Qdisc *qdisc_match_from_root(struct Qdisc *root, u32 handle)
root->handle == handle)
return root;
- hash_for_each_possible_rcu(qdisc_dev(root)->qdisc_hash, q, hash, handle) {
+ hash_for_each_possible_rcu(qdisc_dev(root)->qdisc_hash, q, hash, handle,
+ lockdep_rtnl_is_held()) {
if (q->handle == handle)
return q;
}
