On Thu, May 21, 2015, at 11:51, Konstantin Khlebnikov wrote: > On 20.05.2015 02:33, Mahesh Bandewar wrote: > > On Thu, May 14, 2015 at 6:56 AM, Konstantin Khlebnikov > > <[email protected]> wrote: > >> > >> ipvlan_start_xmit() is called with rcu_read_lock_bh() while its internal > >> structures requre normal rcu_read_lock(). > >> > >> Signed-off-by: Konstantin Khlebnikov <[email protected]> > >> > >> --- > >> > >> [ 802.945151] =============================== > >> [ 802.945160] [ INFO: suspicious RCU usage. ] > >> [ 802.945164] 4.1.0-rc3+ #71 Not tainted > >> [ 802.945165] ------------------------------- > >> [ 802.945167] drivers/net/ipvlan/ipvlan.h:103 suspicious > >> rcu_dereference_check() usage! > >> [ 802.945168] > >> [ 802.945168] other info that might help us debug this: > >> [ 802.945168] > >> [ 802.945170] > >> [ 802.945170] rcu_scheduler_active = 1, debug_locks = 1 > >> [ 802.945173] 3 locks held by ping6/3813: > >> [ 802.945174] #0: (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffff81880f72>] > >> rawv6_sendmsg+0x512/0xbb0 > >> [ 802.945197] #1: (rcu_read_lock_bh){......}, at: [<ffffffff8185e577>] > >> ip6_finish_output2+0x57/0x790 > >> [ 802.945205] #2: (rcu_read_lock_bh){......}, at: [<ffffffff8177a68b>] > >> __dev_queue_xmit+0x4b/0x930 > >> [ 802.945218] > >> [ 802.945218] stack backtrace: > >> [ 802.945221] CPU: 2 PID: 3813 Comm: ping6 Not tainted 4.1.0-rc3+ #71 > >> [ 802.945222] Hardware name: OpenStack Foundation OpenStack Nova, BIOS > >> Bochs 01/01/2011 > >> [ 802.945224] 0000000000000001 ffff8800db7b7888 ffffffff819de6f8 > >> 0000000000000007 > >> [ 802.945226] ffff8800db738000 ffff8800db7b78b8 ffffffff810a7f92 > >> ffff880214fc8c00 > >> [ 802.945229] ffff88021595b000 ffff88021595a000 ffff880214adf800 > >> ffff8800db7b7968 > >> [ 802.945232] Call Trace: > >> [ 802.945248] [<ffffffff819de6f8>] dump_stack+0x4c/0x65 > >> [ 802.945253] [<ffffffff810a7f92>] lockdep_rcu_suspicious+0xe2/0x130 > >> [ 802.945265] [<ffffffff815e24ac>] ipvlan_queue_xmit+0x17c/0x5a0 > >> [ 802.945268] [<ffffffff810aa5a4>] ? __lock_is_held+0x54/0x70 > >> [ 802.945271] [<ffffffff815e300c>] ipvlan_start_xmit+0x1c/0x50 > >> [ 802.945272] [<ffffffff8177a117>] dev_hard_start_xmit+0x2f7/0x820 > >> [ 802.945274] [<ffffffff817797b6>] ? netif_skb_features+0xf6/0x1d0 > >> [ 802.945276] [<ffffffff81779b84>] ? > >> validate_xmit_skb.isra.99.part.100+0x24/0x2c0 > >> [ 802.945278] [<ffffffff8177ad04>] __dev_queue_xmit+0x6c4/0x930 > >> [ 802.945280] [<ffffffff8177a68b>] ? __dev_queue_xmit+0x4b/0x930 > >> [ 802.945281] [<ffffffff810a963a>] ? mark_held_locks+0x6a/0x90 > >> [ 802.945283] [<ffffffff8177af8e>] dev_queue_xmit_sk+0xe/0x10 > >> [ 802.945285] [<ffffffff8185e824>] ip6_finish_output2+0x304/0x790 > >> [ 802.945287] [<ffffffff81860dde>] ? ip6_finish_output+0x9e/0x1e0 > >> [ 802.945288] [<ffffffff81860dde>] ip6_finish_output+0x9e/0x1e0 > >> [ 802.945290] [<ffffffff81860fdb>] ip6_output+0xbb/0x180 > >> [ 802.945302] [<ffffffff818a7d0a>] ? ip6_find_1stfragopt+0x9a/0xa0 > >> [ 802.945304] [<ffffffff81860d40>] ? ip6_fragment+0xe80/0xe80 > >> [ 802.945306] [<ffffffff818a805c>] ip6_local_out_sk+0x2c/0x70 > >> [ 802.945308] [<ffffffff818a80b0>] ip6_local_out+0x10/0x20 > >> [ 802.945309] [<ffffffff81861571>] ip6_send_skb+0x31/0xd0 > >> [ 802.945311] [<ffffffff81861644>] ip6_push_pending_frames+0x34/0x40 > >> [ 802.945313] [<ffffffff81881368>] rawv6_sendmsg+0x908/0xbb0 > >> [ 802.945328] [<ffffffff810aa5a4>] ? __lock_is_held+0x54/0x70 > >> [ 802.945340] [<ffffffff81817e9e>] inet_sendmsg+0x10e/0x1f0 > >> [ 802.945343] [<ffffffff81817d90>] ? inet_recvmsg+0x200/0x200 > >> [ 802.945351] [<ffffffff81758275>] sock_sendmsg+0x45/0x50 > >> [ 802.945354] [<ffffffff8175a719>] SYSC_sendto+0xd9/0x110 > >> [ 802.945357] [<ffffffff8175ac99>] SyS_sendto+0x9/0x10 > >> [ 802.945362] [<ffffffff819ebfae>] system_call_fastpath+0x12/0x76 > >> --- > >> drivers/net/ipvlan/ipvlan_main.c | 4 ++++ > >> 1 file changed, 4 insertions(+) > >> > >> diff --git a/drivers/net/ipvlan/ipvlan_main.c > >> b/drivers/net/ipvlan/ipvlan_main.c > >> index 77b92a0fe557..0cafd3e6f02d 100644 > >> --- a/drivers/net/ipvlan/ipvlan_main.c > >> +++ b/drivers/net/ipvlan/ipvlan_main.c > >> @@ -173,6 +173,7 @@ static int ipvlan_stop(struct net_device *dev) > >> return 0; > >> } > >> > >> +/* called with rcu_read_lock_bh. */ > >> static netdev_tx_t ipvlan_start_xmit(struct sk_buff *skb, > >> struct net_device *dev) > >> { > >> @@ -180,6 +181,7 @@ static netdev_tx_t ipvlan_start_xmit(struct sk_buff > >> *skb, > >> int skblen = skb->len; > >> int ret; > >> > >> + rcu_read_lock(); > > > > I don't believe this is correct. The correct way would be the way it > > is fixed in the following patch - > > https://patchwork.ozlabs.org/patch/471481/ > > I'm not sure, that might just plug the warning without fixing problem. > The rest code uses call_rcu()/synchronize_rcu(). Probably relation > between quiescent states of rcu and rcu_bh isn't that easy. >
In theory both, rcu_read_lock and rcu_read_lock_bh must be held, otherwise call_rcu would be allowed to execute callback if no rcu_read_lock but only rcu_read_lock_bh is taken. *AFAIK* in normal kernels, grace period for call_rcu is just longer, call_rcu_bh does check transition from and to softirqs. Bye, Hannes -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
