diff mbox series

[net] ipv4: Silence suspicious RCU usage warning

Message ID 20200729083713.2051435-1-idosch@idosch.org
State Accepted
Delegated to: David Miller
Headers show
Series [net] ipv4: Silence suspicious RCU usage warning | expand

Commit Message

Ido Schimmel July 29, 2020, 8:37 a.m. UTC 
From: Ido Schimmel <idosch@mellanox.com>

fib_trie_unmerge() is called with RTNL held, but not from an RCU
read-side critical section. This leads to the following warning [1] when
the FIB alias list in a leaf is traversed with
hlist_for_each_entry_rcu().

Since the function is always called with RTNL held and since
modification of the list is protected by RTNL, simply use
hlist_for_each_entry() and silence the warning.

[1]
WARNING: suspicious RCU usage
5.8.0-rc4-custom-01520-gc1f937f3f83b #30 Not tainted
-----------------------------
net/ipv4/fib_trie.c:1867 RCU-list traversed in non-reader section!!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
1 lock held by ip/164:
 #0: ffffffff85a27850 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x49a/0xbd0

stack backtrace:
CPU: 0 PID: 164 Comm: ip Not tainted 5.8.0-rc4-custom-01520-gc1f937f3f83b #30
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-2.fc32 04/01/2014
Call Trace:
 dump_stack+0x100/0x184
 lockdep_rcu_suspicious+0x153/0x15d
 fib_trie_unmerge+0x608/0xdb0
 fib_unmerge+0x44/0x360
 fib4_rule_configure+0xc8/0xad0
 fib_nl_newrule+0x37a/0x1dd0
 rtnetlink_rcv_msg+0x4f7/0xbd0
 netlink_rcv_skb+0x17a/0x480
 rtnetlink_rcv+0x22/0x30
 netlink_unicast+0x5ae/0x890
 netlink_sendmsg+0x98a/0xf40
 ____sys_sendmsg+0x879/0xa00
 ___sys_sendmsg+0x122/0x190
 __sys_sendmsg+0x103/0x1d0
 __x64_sys_sendmsg+0x7d/0xb0
 do_syscall_64+0x54/0xa0
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7fc80a234e97
Code: Bad RIP value.
RSP: 002b:00007ffef8b66798 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fc80a234e97
RDX: 0000000000000000 RSI: 00007ffef8b66800 RDI: 0000000000000003
RBP: 000000005f141b1c R08: 0000000000000001 R09: 0000000000000000
R10: 00007fc80a2a8ac0 R11: 0000000000000246 R12: 0000000000000001
R13: 0000000000000000 R14: 00007ffef8b67008 R15: 0000556fccb10020

Fixes: 0ddcf43d5d4a ("ipv4: FIB Local/MAIN table collapse")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
---
 net/ipv4/fib_trie.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

David Miller July 29, 2020, 7:13 p.m. UTC | #1 
From: Ido Schimmel <idosch@idosch.org>
Date: Wed, 29 Jul 2020 11:37:13 +0300

> From: Ido Schimmel <idosch@mellanox.com>
> 
> fib_trie_unmerge() is called with RTNL held, but not from an RCU
> read-side critical section. This leads to the following warning [1] when
> the FIB alias list in a leaf is traversed with
> hlist_for_each_entry_rcu().
> 
> Since the function is always called with RTNL held and since
> modification of the list is protected by RTNL, simply use
> hlist_for_each_entry() and silence the warning.
> 
> [1]
> WARNING: suspicious RCU usage
> 5.8.0-rc4-custom-01520-gc1f937f3f83b #30 Not tainted
> -----------------------------
> net/ipv4/fib_trie.c:1867 RCU-list traversed in non-reader section!!
 ...
> Fixes: 0ddcf43d5d4a ("ipv4: FIB Local/MAIN table collapse")
> Signed-off-by: Ido Schimmel <idosch@mellanox.com>
> Reviewed-by: Jiri Pirko <jiri@mellanox.com>

Also applied, thanks.
diff mbox series

Patch

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 248f1c1959a6..3c65f71d0e82 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1864,7 +1864,7 @@  struct fib_table *fib_trie_unmerge(struct fib_table *oldtb)
 	while ((l = leaf_walk_rcu(&tp, key)) != NULL) {
 		struct key_vector *local_l = NULL, *local_tp;
 
-		hlist_for_each_entry_rcu(fa, &l->leaf, fa_list) {
+		hlist_for_each_entry(fa, &l->leaf, fa_list) {
 			struct fib_alias *new_fa;
 
 			if (local_tb->tb_id != fa->tb_id)