cxgb4: Not need to hold the adap_rcu_lock lock when read adap_rcu_list

cxgb4_netdev maybe lead to dead lock, since it uses a spin lock, and be called
in both thread and softirq context, but not disable BH, the lockdep report is
below; In fact, cxgb4_netdev only reads adap_rcu_list with RCU protection, so
not need to hold spin lock again.
	=================================
	[ INFO: inconsistent lock state ]
	3.14.7+ #24 Tainted: G         C O
	---------------------------------
	inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
	radvd/3794 [HC0[0]:SC1[1]:HE1:SE0] takes:
	 (adap_rcu_lock){+.?...}, at: [<ffffffffa09989ea>] clip_add+0x2c/0x116 [cxgb4]
	{SOFTIRQ-ON-W} state was registered at:
	  [<ffffffff810fca81>] __lock_acquire+0x34a/0xe48
	  [<ffffffff810fd98b>] lock_acquire+0x82/0x9d
	  [<ffffffff815d6ff8>] _raw_spin_lock+0x34/0x43
	  [<ffffffffa09989ea>] clip_add+0x2c/0x116 [cxgb4]
	  [<ffffffffa0998beb>] cxgb4_inet6addr_handler+0x117/0x12c [cxgb4]
	  [<ffffffff815da98b>] notifier_call_chain+0x32/0x5c
	  [<ffffffff815da9f9>] __atomic_notifier_call_chain+0x44/0x6e
	  [<ffffffff815daa32>] atomic_notifier_call_chain+0xf/0x11
	  [<ffffffff815b1356>] inet6addr_notifier_call_chain+0x16/0x18
	  [<ffffffffa01f72e5>] ipv6_add_addr+0x404/0x46e [ipv6]
	  [<ffffffffa01f8df0>] addrconf_add_linklocal+0x5f/0x95 [ipv6]
	  [<ffffffffa01fc3e9>] addrconf_notify+0x632/0x841 [ipv6]
	  [<ffffffff815da98b>] notifier_call_chain+0x32/0x5c
	  [<ffffffff810e09a1>] __raw_notifier_call_chain+0x9/0xb
	  [<ffffffff810e09b2>] raw_notifier_call_chain+0xf/0x11
	  [<ffffffff8151b3b7>] call_netdevice_notifiers_info+0x4e/0x56
	  [<ffffffff8151b3d0>] call_netdevice_notifiers+0x11/0x13
	  [<ffffffff8151c0a6>] netdev_state_change+0x1f/0x38
	  [<ffffffff8152f004>] linkwatch_do_dev+0x3b/0x49
	  [<ffffffff8152f184>] __linkwatch_run_queue+0x10b/0x144
	  [<ffffffff8152f1dd>] linkwatch_event+0x20/0x27
	  [<ffffffff810d7bc0>] process_one_work+0x1cb/0x2ee
	  [<ffffffff810d7e3b>] worker_thread+0x12e/0x1fc
	  [<ffffffff810dd391>] kthread+0xc4/0xcc
	  [<ffffffff815dc48c>] ret_from_fork+0x7c/0xb0
	irq event stamp: 3388
	hardirqs last  enabled at (3388): [<ffffffff810c6c85>]
	__local_bh_enable_ip+0xaa/0xd9
	hardirqs last disabled at (3387): [<ffffffff810c6c2d>]
	__local_bh_enable_ip+0x52/0xd9
	softirqs last  enabled at (3288): [<ffffffffa01f1d5b>]
	rcu_read_unlock_bh+0x0/0x2f [ipv6]
	softirqs last disabled at (3289): [<ffffffff815ddafc>]
	do_softirq_own_stack+0x1c/0x30

	other info that might help us debug this:
	 Possible unsafe locking scenario:

	       CPU0
	       ----
	  lock(adap_rcu_lock);
	  <Interrupt>
	    lock(adap_rcu_lock);

	 *** DEADLOCK ***

	5 locks held by radvd/3794:
	 #0:  (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffffa020b85a>]
	rawv6_sendmsg+0x74b/0xa4d [ipv6]
	 #1:  (rcu_read_lock){.+.+..}, at: [<ffffffff8151ac6b>]
	rcu_lock_acquire+0x0/0x29
	 #2:  (rcu_read_lock){.+.+..}, at: [<ffffffffa01f4cca>]
	rcu_lock_acquire.constprop.16+0x0/0x30 [ipv6]
	 #3:  (rcu_read_lock){.+.+..}, at: [<ffffffff810e09b4>]
	rcu_lock_acquire+0x0/0x29
	 #4:  (rcu_read_lock){.+.+..}, at: [<ffffffffa0998782>]
	rcu_lock_acquire.constprop.40+0x0/0x30 [cxgb4]

	stack backtrace:
	CPU: 7 PID: 3794 Comm: radvd Tainted: G         C O 3.14.7+ #24
	Hardware name: Supermicro X7DBU/X7DBU, BIOS 6.00 12/03/2007
	 ffffffff81f15990 ffff88012fdc36a8 ffffffff815d0016 0000000000000006
	 ffff8800c80dc2a0 ffff88012fdc3708 ffffffff815cc727 0000000000000001
	 0000000000000001 ffff880100000000 ffffffff81015b02 ffff8800c80dcb58
	Call Trace:
	 <IRQ>  [<ffffffff815d0016>] dump_stack+0x4e/0x71
	 [<ffffffff815cc727>] print_usage_bug+0x1ec/0x1fd
	 [<ffffffff81015b02>] ? save_stack_trace+0x27/0x44
	 [<ffffffff810fbfaa>] ? check_usage_backwards+0xa0/0xa0
	 [<ffffffff810fc640>] mark_lock+0x11b/0x212
	 [<ffffffff810fca0b>] __lock_acquire+0x2d4/0xe48
	 [<ffffffff810fbfaa>] ? check_usage_backwards+0xa0/0xa0
	 [<ffffffff810fbff6>] ? check_usage_forwards+0x4c/0xa6
	 [<ffffffff810c6c8a>] ? __local_bh_enable_ip+0xaf/0xd9
	 [<ffffffff810fd98b>] lock_acquire+0x82/0x9d
	 [<ffffffffa09989ea>] ? clip_add+0x2c/0x116 [cxgb4]
	 [<ffffffffa0998782>] ? rcu_read_unlock+0x23/0x23 [cxgb4]
	 [<ffffffff815d6ff8>] _raw_spin_lock+0x34/0x43
	 [<ffffffffa09989ea>] ? clip_add+0x2c/0x116 [cxgb4]
	 [<ffffffffa09987b0>] ? rcu_lock_acquire.constprop.40+0x2e/0x30 [cxgb4]
	 [<ffffffffa0998782>] ? rcu_read_unlock+0x23/0x23 [cxgb4]
	 [<ffffffffa09989ea>] clip_add+0x2c/0x116 [cxgb4]
	 [<ffffffffa0998beb>] cxgb4_inet6addr_handler+0x117/0x12c [cxgb4]
	 [<ffffffff810fd99d>] ? lock_acquire+0x94/0x9d
	 [<ffffffff810e09b4>] ? raw_notifier_call_chain+0x11/0x11
	 [<ffffffff815da98b>] notifier_call_chain+0x32/0x5c
	 [<ffffffff815da9f9>] __atomic_notifier_call_chain+0x44/0x6e
	 [<ffffffff815daa32>] atomic_notifier_call_chain+0xf/0x11
	 [<ffffffff815b1356>] inet6addr_notifier_call_chain+0x16/0x18
	 [<ffffffffa01f72e5>] ipv6_add_addr+0x404/0x46e [ipv6]
	 [<ffffffff810fde6a>] ? trace_hardirqs_on+0xd/0xf
	 [<ffffffffa01fb634>] addrconf_prefix_rcv+0x385/0x6ea [ipv6]
	 [<ffffffffa0207950>] ndisc_rcv+0x9d3/0xd76 [ipv6]
	 [<ffffffffa020d536>] icmpv6_rcv+0x592/0x67b [ipv6]
	 [<ffffffff810c6c85>] ? __local_bh_enable_ip+0xaa/0xd9
	 [<ffffffff810c6c85>] ? __local_bh_enable_ip+0xaa/0xd9
	 [<ffffffff810fd8dc>] ? lock_release+0x14e/0x17b
	 [<ffffffffa020df97>] ? rcu_read_unlock+0x21/0x23 [ipv6]
	 [<ffffffff8150df52>] ? rcu_read_unlock+0x23/0x23
	 [<ffffffffa01f4ede>] ip6_input_finish+0x1e4/0x2fc [ipv6]
	 [<ffffffffa01f540b>] ip6_input+0x33/0x38 [ipv6]
	 [<ffffffffa01f5557>] ip6_mc_input+0x147/0x160 [ipv6]
	 [<ffffffffa01f4ba3>] ip6_rcv_finish+0x7c/0x81 [ipv6]
	 [<ffffffffa01f5397>] ipv6_rcv+0x3a1/0x3e2 [ipv6]
	 [<ffffffff8151ef96>] __netif_receive_skb_core+0x4ab/0x511
	 [<ffffffff810fdc94>] ? mark_held_locks+0x71/0x99
	 [<ffffffff8151f0c0>] ? process_backlog+0x69/0x15e
	 [<ffffffff8151f045>] __netif_receive_skb+0x49/0x5b
	 [<ffffffff8151f0cf>] process_backlog+0x78/0x15e
	 [<ffffffff8151f571>] ? net_rx_action+0x1a2/0x1cc
	 [<ffffffff8151f47b>] net_rx_action+0xac/0x1cc
	 [<ffffffff810c69b7>] ? __do_softirq+0xad/0x218
	 [<ffffffff810c69ff>] __do_softirq+0xf5/0x218
	 [<ffffffff815ddafc>] do_softirq_own_stack+0x1c/0x30
	 <EOI>  [<ffffffff810c6bb6>] do_softirq+0x38/0x5d
	 [<ffffffffa01f1d5b>] ? ip6_copy_metadata+0x156/0x156 [ipv6]
	 [<ffffffff810c6c78>] __local_bh_enable_ip+0x9d/0xd9
	 [<ffffffffa01f1d88>] rcu_read_unlock_bh+0x2d/0x2f [ipv6]
	 [<ffffffffa01f28b4>] ip6_finish_output2+0x381/0x3d8 [ipv6]
	 [<ffffffffa01f49ef>] ip6_finish_output+0x6e/0x73 [ipv6]
	 [<ffffffffa01f4a70>] ip6_output+0x7c/0xa8 [ipv6]
	 [<ffffffff815b1bfa>] dst_output+0x18/0x1c
	 [<ffffffff815b1c9e>] ip6_local_out+0x1c/0x21
	 [<ffffffffa01f2489>] ip6_push_pending_frames+0x37d/0x427 [ipv6]
	 [<ffffffff81558af8>] ? skb_orphan+0x39/0x39
	 [<ffffffffa020b85a>] ? rawv6_sendmsg+0x74b/0xa4d [ipv6]
	 [<ffffffffa020ba51>] rawv6_sendmsg+0x942/0xa4d [ipv6]
	 [<ffffffff81584cd2>] inet_sendmsg+0x3d/0x66
	 [<ffffffff81508930>] __sock_sendmsg_nosec+0x25/0x27
	 [<ffffffff8150b0d7>] sock_sendmsg+0x5a/0x7b
	 [<ffffffff810fd8dc>] ? lock_release+0x14e/0x17b
	 [<ffffffff8116d756>] ? might_fault+0x9e/0xa5
	 [<ffffffff8116d70d>] ? might_fault+0x55/0xa5
	 [<ffffffff81508cb1>] ? copy_from_user+0x2a/0x2c
	 [<ffffffff8150b70c>] ___sys_sendmsg+0x226/0x2d9
	 [<ffffffff810fcd25>] ? __lock_acquire+0x5ee/0xe48
	 [<ffffffff810fde01>] ? trace_hardirqs_on_caller+0x145/0x1a1
	 [<ffffffff8118efcb>] ? slab_free_hook.isra.71+0x50/0x59
	 [<ffffffff8115c81f>] ? release_pages+0xbc/0x181
	 [<ffffffff810fd99d>] ? lock_acquire+0x94/0x9d
	 [<ffffffff81115e97>] ? read_seqcount_begin.constprop.25+0x73/0x90
	 [<ffffffff8150c408>] __sys_sendmsg+0x3d/0x5b
	 [<ffffffff8150c433>] SyS_sendmsg+0xd/0x19
	 [<ffffffff815dc53d>] system_call_fastpath+0x1a/0x1f

Reported-by: Ben Greear <greearb@candelatech.com>
Cc: Casey Leedom <leedom@chelsio.com>
Cc: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Casey Leedom <leedom@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c

@@ -4057,22 +4057,19 @@ int cxgb4_unregister_uld(enum cxgb4_uld type)
 EXPORT_SYMBOL(cxgb4_unregister_uld);
 
 /* Check if netdev on which event is occured belongs to us or not. Return
- * suceess (1) if it belongs otherwise failure (0).
+ * success (true) if it belongs otherwise failure (false).
+ * Called with rcu_read_lock() held.
  */
-static int cxgb4_netdev(struct net_device *netdev)
+static bool cxgb4_netdev(const struct net_device *netdev)
 {
 	struct adapter *adap;
 	int i;
 
-	spin_lock(&adap_rcu_lock);
 	list_for_each_entry_rcu(adap, &adap_rcu_list, rcu_node)
 		for (i = 0; i < MAX_NPORTS; i++)
-			if (adap->port[i] == netdev) {
-				spin_unlock(&adap_rcu_lock);
-				return 1;
-			}
-	spin_unlock(&adap_rcu_lock);
-	return 0;
+			if (adap->port[i] == netdev)
+				return true;
+	return false;
 }
 
 static int clip_add(struct net_device *event_dev, struct inet6_ifaddr *ifa,
@@ -6396,6 +6393,7 @@ static void remove_one(struct pci_dev *pdev)
 			adapter->flags &= ~DEV_ENABLED;
 		}
 		pci_release_regions(pdev);
+		synchronize_rcu();
 		kfree(adapter);
 	} else
 		pci_release_regions(pdev);