Return-Path: <cyrus@holtmann.org>
From: Jukka Rissanen <jukka.rissanen@linux.intel.com>
To: linux-bluetooth@vger.kernel.org
Subject: [PATCH] Bluetooth: Incorrect locking when sending data in softirq
Date: Wed, 15 Oct 2014 15:43:05 +0300
Message-Id: <1413376985-25812-1-git-send-email-jukka.rissanen@linux.intel.com>
Sender: linux-bluetooth-owner@vger.kernel.org
List-ID: <linux-bluetooth.vger.kernel.org>

Use spin_lock_irqsave() when sending data to hci channel. Otherwise
the lockdep gives inconsistent lock state warning when sending data
to 6lowpan channel.

 [ INFO: inconsistent lock state ]
 3.17.0-rc1-bt6lowpan #1 Not tainted
 ---------------------------------
 inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
 kworker/u3:0/321 [HC0[0]:SC0[0]:HE1:SE1] takes:
  (&(&list->lock)->rlock#6){+.?...}, at: [<f845fdac>] hci_send_acl+0xac/0x290 [bluetooth]
 {IN-SOFTIRQ-W} state was registered at:
   [<c10915a3>] __lock_acquire+0x6d3/0x1d20
   [<c109325d>] lock_acquire+0x9d/0x140
   [<c1889c25>] _raw_spin_lock+0x45/0x80
   [<f845fdac>] hci_send_acl+0xac/0x290 [bluetooth]
   [<f8480c60>] l2cap_do_send+0x60/0x100 [bluetooth]
   [<f8484830>] l2cap_chan_send+0x7f0/0x10e0 [bluetooth]
   [<f873191e>] send_pkt+0x4e/0xa0 [bluetooth_6lowpan]
   [<f8731d20>] bt_xmit+0x3b0/0x770 [bluetooth_6lowpan]
   [<c17742f4>] dev_hard_start_xmit+0x344/0x670
   [<c17749ad>] __dev_queue_xmit+0x38d/0x680
   [<c1774caf>] dev_queue_xmit+0xf/0x20
   [<c177b8b0>] neigh_connected_output+0x130/0x1a0
   [<c1812a63>] ip6_finish_output2+0x173/0x8c0
   [<c18182db>] ip6_finish_output+0x7b/0x1b0
   [<c18184a7>] ip6_output+0x97/0x2a0
   [<c183a46b>] mld_sendpack+0x5eb/0x650
   [<c183acc1>] mld_ifc_timer_expire+0x191/0x2f0
   [<c10ac385>] call_timer_fn+0x85/0x1c0
   [<c10acb72>] run_timer_softirq+0x192/0x280
   [<c104fd84>] __do_softirq+0xd4/0x300
   [<c10049fc>] do_softirq_own_stack+0x2c/0x40
   [<c1050136>] irq_exit+0x86/0xb0
   [<c188bd98>] smp_apic_timer_interrupt+0x38/0x50
   [<c188b6ce>] apic_timer_interrupt+0x32/0x38

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
---
Hi,

this patch fixes the locking issue when sending larger amount of
data via 6lowpan link. After this patch the lockdep no longer warns
about softirq issues. 

Cheers,
Jukka


 net/bluetooth/hci_core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 8aea4be..3e295ff 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -4642,6 +4642,7 @@ static void hci_queue_acl(struct hci_chan *chan, struct sk_buff_head *queue,
 	struct hci_conn *conn = chan->conn;
 	struct hci_dev *hdev = conn->hdev;
 	struct sk_buff *list;
+	unsigned long irq_flags;
 
 	skb->len = skb_headlen(skb);
 	skb->data_len = 0;
@@ -4673,7 +4674,7 @@ static void hci_queue_acl(struct hci_chan *chan, struct sk_buff_head *queue,
 		skb_shinfo(skb)->frag_list = NULL;
 
 		/* Queue all fragments atomically */
-		spin_lock(&queue->lock);
+		spin_lock_irqsave(&queue->lock, irq_flags);
 
 		__skb_queue_tail(queue, skb);
 
@@ -4690,7 +4691,7 @@ static void hci_queue_acl(struct hci_chan *chan, struct sk_buff_head *queue,
 			__skb_queue_tail(queue, skb);
 		} while (list);
 
-		spin_unlock(&queue->lock);
+		spin_unlock_irqrestore(&queue->lock, irq_flags);
 	}
 }
 
-- 
1.8.3.1