From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Fainelli Subject: Re: [PATCH net-next 10/10] net: dsa: Add lockdep class to tx queues to avoid lockdep splat Date: Tue, 05 May 2015 16:22:33 -0700 Message-ID: <554950B9.4020807@gmail.com> References: <1430867396-2268-1-git-send-email-andrew@lunn.ch> <1430867396-2268-11-git-send-email-andrew@lunn.ch> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: Andrew Lunn , davem@davemloft.net, linux@roeck-us.net Return-path: Received: from mail-pd0-f172.google.com ([209.85.192.172]:34683 "EHLO mail-pd0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753125AbbEEXWt (ORCPT ); Tue, 5 May 2015 19:22:49 -0400 Received: by pdbqa5 with SMTP id qa5so211641295pdb.1 for ; Tue, 05 May 2015 16:22:48 -0700 (PDT) In-Reply-To: <1430867396-2268-11-git-send-email-andrew@lunn.ch> Sender: netdev-owner@vger.kernel.org List-ID: On 05/05/15 16:09, Andrew Lunn wrote: > DSA stacks an Ethernet device on top of an Ethernet device. This can > cause false positive lockdep splats for the transmit queue: > > ============================================= > [ INFO: possible recursive locking detected ] > 4.0.0-rc7-01838-g70621a215fc7 #386 Not tainted > --------------------------------------------- > kworker/0:0/4 is trying to acquire lock: > (_xmit_ETHER#2){+.-...}, at: [] sch_direct_xmit+0xa8/0x1fc > > but task is already holding lock: > (_xmit_ETHER#2){+.-...}, at: [] __dev_queue_xmit+0x4d4/0x56c > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(_xmit_ETHER#2); > lock(_xmit_ETHER#2); > > To avoid this, walk the tq queues of the dsa slaves and set a lockdep > class. Had meant to fix that a while ago when this was bugging me, thanks for doing this! > > Signed-off-by: Andrew Lunn Acked-by: Florian Fainelli -- Florian