From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Subject: Re: [BUG] Lockdep splat in usb network gadget Date: Wed, 23 Jul 2014 11:11:14 +0200 (CEST) Message-ID: References: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: netdev , linux-usb@vger.kernel.org, jeff.westfahl@ni.com To: Li RongQing Return-path: Received: from www.linutronix.de ([62.245.132.108]:43248 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757551AbaGWJLR (ORCPT ); Wed, 23 Jul 2014 05:11:17 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 23 Jul 2014, Li RongQing wrote: > This commit introduced this bug > > commit a9232076374334ca2bc2a448dfde96d38a54349a > Author: Jeff Westfahl > Date: Thu May 29 09:49:41 2014 +0300 > > usb: gadget: u_ether: synchronize with transmit when stopping queue > > When disconnecting, it's possible that another thread has already made it > into eth_start_xmit before we call netif_stop_queue. This can lead to a > crash as eth_start_xmit tries to use resources that gether_disconnect is > freeing. Use netif_tx_lock/unlock around netif_stop_queue to ensure no > threads are executing during the remainder of gether_disconnect. > > Signed-off-by: Jeff Westfahl > Tested-by: Jaeden Amero > Signed-off-by: Felipe Balbi So what's the fix? > diff --git a/drivers/usb/gadget/u_ether.c b/drivers/usb/gadget/u_ether.c > index 3d78a88..97b0277 100644 > --- a/drivers/usb/gadget/u_ether.c > +++ b/drivers/usb/gadget/u_ether.c > @@ -1120,7 +1120,10 @@ void gether_disconnect(struct gether *link) > > DBG(dev, "%s\n", __func__); > > + netif_tx_lock(dev->net); > netif_stop_queue(dev->net); > + netif_tx_unlock(dev->net); > + > netif_carrier_off(dev->net);