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| author | Jiri Pirko <jiri@mellanox.com> | 2020-07-20 10:10:41 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2020-07-20 17:00:02 -0700 |
| commit | a8b7b2d0b3fc965d823e362840e5451e2eb4a71b (patch) | |
| tree | 942fba683f866d7c8b2541cd3dfb77e18f4b927e | |
| parent | d89d8d4db48b42d22c5b0e0e8a3f82dd00262c44 (diff) | |
| download | lwn-a8b7b2d0b3fc965d823e362840e5451e2eb4a71b.tar.gz lwn-a8b7b2d0b3fc965d823e362840e5451e2eb4a71b.zip | |
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.h | 4 | ||||
| -rw-r--r-- | net/sched/sch_api.c | 3 |
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; } |