[PATCH 1/2 V3] kaweth: Fix locking to be SMP-safe

[PATCH 1/2 V3] kaweth: Fix locking to be SMP-safe

[Larry Finger]

On an SMP system, the following message is printed. The patch below gets
fixes the problem.

=================================
[ INFO: inconsistent lock state ]
2.6.29-Linus-05093-gc31f403 #57
---------------------------------
inconsistent {hardirq-on-W} -> {in-hardirq-W} usage.
bash/4105 [HC1[1]:SC0[0]:HE0:SE1] takes:
 (&kaweth->device_lock){+...}, at: [<ffffffffa01aa286>]
                 kaweth_usb_receive+0x77/0x1af [kaw eth]
{hardirq-on-W} state was registered at:
  [<ffffffff80260503>] __lock_acquire+0x753/0x1685
  [<ffffffff8026148a>] lock_acquire+0x55/0x71
  [<ffffffff80461ba6>] _spin_lock+0x31/0x3d
  [<ffffffffa01aaa0c>] kaweth_start_xmit+0x2b/0x1e1 [kaweth]
  [<ffffffff803eccd3>] dev_hard_start_xmit+0x22e/0x2ad
  [<ffffffff803fe120>] __qdisc_run+0xf2/0x203
  [<ffffffff803ed0cd>] dev_queue_xmit+0x263/0x39b
  [<ffffffffa03a47cb>] packet_sendmsg_spkt+0x1c4/0x20a [af_packet]
  [<ffffffff803de0c2>] sock_sendmsg+0xe4/0xfd
  [<ffffffff803dec8f>] sys_sendto+0xe4/0x10c
  [<ffffffff8020bccb>] system_call_fastpath+0x16/0x1b
  [<ffffffffffffffff>] 0xffffffffffffffff
irq event stamp: 1280
hardirqs last  enabled at (1279): [<ffffffff80461a71>]
                  _spin_unlock_irqrestore+0x44/0x4c
hardirqs last disabled at (1280): [<ffffffff8020bad7>]
                  save_args+0x67/0x70
softirqs last  enabled at (660): [<ffffffff8024192c>]
                  __do_softirq+0x14d/0x15d
softirqs last disabled at (651): [<ffffffff8020ce9c>]
                  call_softirq+0x1c/0x28

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Stable <stable@kernel.org>
---

DaveM,

I had expected this to be 2.6.31 material, but Oliver requested that it be
sent to Stable as well.

Larry
---

Index: wireless-testing/drivers/net/usb/kaweth.c
===================================================================
--- wireless-testing.orig/drivers/net/usb/kaweth.c
+++ wireless-testing/drivers/net/usb/kaweth.c
@@ -36,7 +36,6 @@
  * Run test procedures
  * Fix bugs from previous two steps
  * Snoop other OSs for any tricks we're not doing
- * SMP locking
  * Reduce arbitrary timeouts
  * Smart multicast support
  * Temporary MAC change support
@@ -796,7 +795,7 @@ static int kaweth_start_xmit(struct sk_b
 
 	int res;
 
-	spin_lock(&kaweth->device_lock);
+	spin_lock_irq(&kaweth->device_lock);
 
 	kaweth_async_set_rx_mode(kaweth);
 	netif_stop_queue(net);
@@ -814,7 +813,7 @@ static int kaweth_start_xmit(struct sk_b
 		if (!copied_skb) {
 			kaweth->stats.tx_errors++;
 			netif_start_queue(net);
-			spin_unlock(&kaweth->device_lock);
+			spin_unlock_irq(&kaweth->device_lock);
 			return 0;
 		}
 	}
@@ -848,7 +847,7 @@ skip:
 		net->trans_start = jiffies;
 	}
 
-	spin_unlock(&kaweth->device_lock);
+	spin_unlock_irq(&kaweth->device_lock);
 
 	return 0;
 }

Re: [PATCH 1/2 V3] kaweth: Fix locking to be SMP-safe

[David Miller]

From: Larry Finger <Larry.Finger@lwfinger.net>
Date: Wed, 01 Apr 2009 10:28:29 -0500

> On an SMP system, the following message is printed. The patch below gets
> fixes the problem.
 ...

> Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
 ...
> I had expected this to be 2.6.31 material, but Oliver requested that it be
> sent to Stable as well.

Applied, thanks.

Re: [PATCH 1/2 V3] kaweth: Fix locking to be SMP-safe

[Herbert Xu]

Larry Finger <Larry.Finger@lwfinger.net> wrote:
>
> @@ -796,7 +795,7 @@ static int kaweth_start_xmit(struct sk_b
> 
>        int res;
> 
> -       spin_lock(&kaweth->device_lock);
> +       spin_lock_irq(&kaweth->device_lock);

Should be irqsave unless you don't expect to be called via netpoll.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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Re: [PATCH 1/2 V3] kaweth: Fix locking to be SMP-safe

[Larry Finger]

Herbert Xu wrote:
> Larry Finger <Larry.Finger@lwfinger.net> wrote:
>> @@ -796,7 +795,7 @@ static int kaweth_start_xmit(struct sk_b
>>
>>        int res;
>>
>> -       spin_lock(&kaweth->device_lock);
>> +       spin_lock_irq(&kaweth->device_lock);
> 
> Should be irqsave unless you don't expect to be called via netpoll.

The .ndo_poll_controller callback is left at NULL in this driver. I believe the
patch to be OK.

Larry

Re: [PATCH 1/2 V3] kaweth: Fix locking to be SMP-safe

[Herbert Xu]

On Thu, Apr 02, 2009 at 10:02:18AM -0500, Larry Finger wrote:
>
> The .ndo_poll_controller callback is left at NULL in this driver. I believe the
> patch to be OK.

Good point!

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt