[PATCH v2 5/5] ath10k: Fix deadlock when peer cannot be created.

[greearb at candelatech.com]

From: Ben Greear <greearb at candelatech.com>

We must not attempt to send WMI packets while holding the data-lock,
as it may deadlock:

BUG: sleeping function called from invalid context at drivers/net/wireless/ath/ath10k/wmi.c:1824
in_atomic(): 1, irqs_disabled(): 0, pid: 2878, name: wpa_supplicant

=============================================
[ INFO: possible recursive locking detected ]
4.4.6+ #21 Tainted: G        W  O
---------------------------------------------
wpa_supplicant/2878 is trying to acquire lock:
 (&(&ar->data_lock)->rlock){+.-...}, at: [<ffffffffa0721511>] ath10k_wmi_tx_beacons_iter+0x26/0x11a [ath10k_core]

but task is already holding lock:
 (&(&ar->data_lock)->rlock){+.-...}, at: [<ffffffffa070251b>] ath10k_peer_create+0x122/0x1ae [ath10k_core]

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

       CPU0
       ----
  lock(&(&ar->data_lock)->rlock);
  lock(&(&ar->data_lock)->rlock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

4 locks held by wpa_supplicant/2878:
 #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff816493ca>] rtnl_lock+0x12/0x14
 #1:  (&ar->conf_mutex){+.+.+.}, at: [<ffffffffa0706932>] ath10k_add_interface+0x3b/0xbda [ath10k_core]
 #2:  (&(&ar->data_lock)->rlock){+.-...}, at: [<ffffffffa070251b>] ath10k_peer_create+0x122/0x1ae [ath10k_core]
 #3:  (rcu_read_lock){......}, at: [<ffffffffa062f304>] rcu_read_lock+0x0/0x66 [mac80211]

stack backtrace:
CPU: 3 PID: 2878 Comm: wpa_supplicant Tainted: G        W  O    4.4.6+ #21
Hardware name: To be filled by O.E.M. To be filled by O.E.M./ChiefRiver, BIOS 4.6.5 06/07/2013
 0000000000000000 ffff8801fcadf8f0 ffffffff8137086d ffffffff82681720
 ffffffff82681720 ffff8801fcadf9b0 ffffffff8112e3be ffff8801fcadf920
 0000000100000000 ffffffff82681720 ffffffffa0721500 ffff8801fcb8d348
Call Trace:
 [<ffffffff8137086d>] dump_stack+0x81/0xb6
 [<ffffffff8112e3be>] __lock_acquire+0xc5b/0xde7
 [<ffffffffa0721500>] ? ath10k_wmi_tx_beacons_iter+0x15/0x11a [ath10k_core]
 [<ffffffff8112d0d0>] ? mark_lock+0x24/0x201
 [<ffffffff8112e908>] lock_acquire+0x132/0x1cb
 [<ffffffff8112e908>] ? lock_acquire+0x132/0x1cb
 [<ffffffffa0721511>] ? ath10k_wmi_tx_beacons_iter+0x26/0x11a [ath10k_core]
 [<ffffffffa07214eb>] ? ath10k_wmi_cmd_send_nowait+0x1ce/0x1ce [ath10k_core]
 [<ffffffff816f9e2b>] _raw_spin_lock_bh+0x31/0x40
 [<ffffffffa0721511>] ? ath10k_wmi_tx_beacons_iter+0x26/0x11a [ath10k_core]
 [<ffffffffa0721511>] ath10k_wmi_tx_beacons_iter+0x26/0x11a [ath10k_core]
 [<ffffffffa07214eb>] ? ath10k_wmi_cmd_send_nowait+0x1ce/0x1ce [ath10k_core]
 [<ffffffffa062eb18>] __iterate_interfaces+0x9d/0x13d [mac80211]
 [<ffffffffa062f609>] ieee80211_iterate_active_interfaces_atomic+0x32/0x3e [mac80211]
 [<ffffffffa07214eb>] ? ath10k_wmi_cmd_send_nowait+0x1ce/0x1ce [ath10k_core]
 [<ffffffffa071fa9f>] ath10k_wmi_tx_beacons_nowait.isra.13+0x14/0x16 [ath10k_core]
 [<ffffffffa0721676>] ath10k_wmi_cmd_send+0x71/0x242 [ath10k_core]
 [<ffffffffa07023f6>] ath10k_wmi_peer_delete+0x3f/0x42 [ath10k_core]
 [<ffffffffa0702557>] ath10k_peer_create+0x15e/0x1ae [ath10k_core]
 [<ffffffffa0707004>] ath10k_add_interface+0x70d/0xbda [ath10k_core]
 [<ffffffffa05fffcc>] drv_add_interface+0x123/0x1a5 [mac80211]
 [<ffffffffa061554b>] ieee80211_do_open+0x351/0x667 [mac80211]
 [<ffffffffa06158aa>] ieee80211_open+0x49/0x4c [mac80211]
 [<ffffffff8163ecf9>] __dev_open+0x88/0xde
 [<ffffffff8163ef6e>] __dev_change_flags+0xa4/0x13a
 [<ffffffff8163f023>] dev_change_flags+0x1f/0x54
 [<ffffffff816a5532>] devinet_ioctl+0x2b9/0x5c9
 [<ffffffff816514dd>] ? copy_to_user+0x32/0x38
 [<ffffffff816a6115>] inet_ioctl+0x81/0x9d
 [<ffffffff816a6115>] ? inet_ioctl+0x81/0x9d
 [<ffffffff81621cf8>] sock_do_ioctl+0x20/0x3d
 [<ffffffff816223c4>] sock_ioctl+0x222/0x22e
 [<ffffffff8121cf95>] do_vfs_ioctl+0x453/0x4d7
 [<ffffffff81625603>] ? __sys_recvmsg+0x4c/0x5b
 [<ffffffff81225af1>] ? __fget_light+0x48/0x6c
 [<ffffffff8121d06b>] SyS_ioctl+0x52/0x74
 [<ffffffff816fa736>] entry_SYSCALL_64_fastpath+0x16/0x7a

Signed-off-by: Ben Greear <greearb at candelatech.com>
---
 drivers/net/wireless/ath/ath10k/mac.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
index 020dd25..be8345c 100644
--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c
@@ -700,10 +700,10 @@ static int ath10k_peer_create(struct ath10k *ar,
 
 	peer = ath10k_peer_find(ar, vdev_id, addr);
 	if (!peer) {
+		spin_unlock_bh(&ar->data_lock);
 		ath10k_warn(ar, "failed to find peer %pM on vdev %i after creation\n",
 			    addr, vdev_id);
 		ath10k_wmi_peer_delete(ar, vdev_id, addr);
-		spin_unlock_bh(&ar->data_lock);
 		return -ENOENT;
 	}
 
-- 
2.4.3