Patch "net/xen-netfront: only napi_synchronize() if running" has been added to the 4.2-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    net/xen-netfront: only napi_synchronize() if running

to the 4.2-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-xen-netfront-only-napi_synchronize-if-running.patch
and it can be found in the queue-4.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 274b045509175db0405c784be85e8cce116e6f7d Mon Sep 17 00:00:00 2001
From: Chas Williams <3chas3@gmail.com>
Date: Thu, 27 Aug 2015 12:28:46 -0400
Subject: net/xen-netfront: only napi_synchronize() if running

From: Chas Williams <3chas3@gmail.com>

commit 274b045509175db0405c784be85e8cce116e6f7d upstream.

If an interface isn't running napi_synchronize() will hang forever.

[  392.248403] rmmod           R  running task        0   359    343 0x00000000
[  392.257671]  ffff88003760fc88 ffff880037193b40 ffff880037193160 ffff88003760fc88
[  392.267644]  ffff880037610000 ffff88003760fcd8 0000000100014c22 ffffffff81f75c40
[  392.277524]  0000000000bc7010 ffff88003760fca8 ffffffff81796927 ffffffff81f75c40
[  392.287323] Call Trace:
[  392.291599]  [<ffffffff81796927>] schedule+0x37/0x90
[  392.298553]  [<ffffffff8179985b>] schedule_timeout+0x14b/0x280
[  392.306421]  [<ffffffff810f91b9>] ? irq_free_descs+0x69/0x80
[  392.314006]  [<ffffffff811084d0>] ? internal_add_timer+0xb0/0xb0
[  392.322125]  [<ffffffff81109d07>] msleep+0x37/0x50
[  392.329037]  [<ffffffffa00ec79a>] xennet_disconnect_backend.isra.24+0xda/0x390 [xen_netfront]
[  392.339658]  [<ffffffffa00ecadc>] xennet_remove+0x2c/0x80 [xen_netfront]
[  392.348516]  [<ffffffff81481c69>] xenbus_dev_remove+0x59/0xc0
[  392.356257]  [<ffffffff814e7217>] __device_release_driver+0x87/0x120
[  392.364645]  [<ffffffff814e7cf8>] driver_detach+0xb8/0xc0
[  392.371989]  [<ffffffff814e6e69>] bus_remove_driver+0x59/0xe0
[  392.379883]  [<ffffffff814e84f0>] driver_unregister+0x30/0x70
[  392.387495]  [<ffffffff814814b2>] xenbus_unregister_driver+0x12/0x20
[  392.395908]  [<ffffffffa00ed89b>] netif_exit+0x10/0x775 [xen_netfront]
[  392.404877]  [<ffffffff81124e08>] SyS_delete_module+0x1d8/0x230
[  392.412804]  [<ffffffff8179a8ee>] system_call_fastpath+0x12/0x71

Signed-off-by: Chas Williams <3chas3@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: "Kamata, Munehisa" <kamatam@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/net/xen-netfront.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1348,7 +1348,8 @@ static void xennet_disconnect_backend(st
 		queue->tx_evtchn = queue->rx_evtchn = 0;
 		queue->tx_irq = queue->rx_irq = 0;
 
-		napi_synchronize(&queue->napi);
+		if (netif_running(info->netdev))
+			napi_synchronize(&queue->napi);
 
 		xennet_release_tx_bufs(queue);
 		xennet_release_rx_bufs(queue);


Patches currently in stable-queue which might be from 3chas3@gmail.com are

queue-4.2/net-xen-netfront-only-napi_synchronize-if-running.patch