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authorJiri Pirko <jiri@mellanox.com>2020-07-20 10:10:41 +0200
committerDavid S. Miller <davem@davemloft.net>2020-07-20 17:00:02 -0700
commita8b7b2d0b3fc965d823e362840e5451e2eb4a71b (patch)
tree942fba683f866d7c8b2541cd3dfb77e18f4b927e
parentd89d8d4db48b42d22c5b0e0e8a3f82dd00262c44 (diff)
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>
-rw-r--r--include/linux/hashtable.h4
-rw-r--r--net/sched/sch_api.c3
2 files changed, 4 insertions, 3 deletions
diff --git a/include/linux/hashtable.h b/include/linux/hashtable.h
index 78b6ea5fa8ba..f6c666730b8c 100644
--- a/include/linux/hashtable.h
+++ b/include/linux/hashtable.h
@@ -173,9 +173,9 @@ static inline void hash_del_rcu(struct hlist_node *node)
* @member: the name of the hlist_node within the struct
* @key: the key of the objects to iterate over
*/
-#define hash_for_each_possible_rcu(name, obj, member, key) \
+#define hash_for_each_possible_rcu(name, obj, member, key, cond...) \
hlist_for_each_entry_rcu(obj, &name[hash_min(key, HASH_BITS(name))],\
- member)
+ member, ## cond)
/**
* hash_for_each_possible_rcu_notrace - iterate over all possible objects hashing
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;
}