From a8b7b2d0b3fc965d823e362840e5451e2eb4a71b Mon Sep 17 00:00:00 2001 From: Jiri Pirko Date: Mon, 20 Jul 2020 10:10:41 +0200 Subject: 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 Signed-off-by: Jiri Pirko Signed-off-by: David S. Miller --- net/sched/sch_api.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'net/sched') diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c index 11ebba60da3b..2a76a2f5ed88 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; } -- cgit v1.2.3