From mboxrd@z Thu Jan 1 00:00:00 1970 From: Or Gerlitz Subject: Re: hitting lockdep warning as of too early VF probe with 3.9-rc1 Date: Wed, 17 Apr 2013 18:14:48 +0300 Message-ID: <516EBC68.1090802@mellanox.com> References: <51360D7C.3060209@mellanox.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Cc: Or Gerlitz , Greg Kroah-Hartman , David Miller , Roland Dreier , netdev , Yan Burman , Jack Morgenstein , "Michael S. Tsirkin" , Don Dutile , Tejun Heo To: Ming Lei Return-path: Received: from eu1sys200aog110.obsmtp.com ([207.126.144.129]:32928 "EHLO eu1sys200aog110.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966603Ab3DQPPI (ORCPT ); Wed, 17 Apr 2013 11:15:08 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On 07/03/2013 04:03, Ming Lei wrote: > On Thu, Mar 7, 2013 at 4:54 AM, Or Gerlitz wrote: >> On Wed, Mar 6, 2013 at 4:43 AM, Ming Lei wrote: >>> You are adding one new PCI device inside another PCI device's probe(), >>> so the new device will be probed, since PCI probe() is scheduled by >>> work_on_cpu, then cause flush_work() called inside worker function, >>> which might be a real deadlock. >> So if I understand correct, you recommend to somehow avoid this nested probing? > Yes, you might need to avoid the nested probing in your driver. > >>> I am wondering why this commit can cause the problem, since the PCI >>> device will be probed with its driver if there is one driver for it. There is no >>> any limit on when the driver should be loaded into system, either before >>> device is added or after. >> FWIW to undertstanding the issue - the same driver (mlx4_core) is used >> by the PF and VF, so the VF driver is already loaded at the time its >> been added as new PCI device. >> >>> From driver core view, looks no wrong things are found. >> So this got me confused, you pointed on possible deadlock, are you >> saying the deadlock wouldn't be the result of how the driver code is >> going nor the commited we bisected? > My commit only affects the driver loading path, but your warning > is hit in driver probe path triggered by device addition, so the lockdep > warning should still be triggered without my commit since the two paths > are totally independent, right? If this is the case, I am not sure how come we never saw this warning before 3.9-rc1 which introduced your commit 190888ac01d059e38ffe77a2291d44cafa9016fb "driver core: fix possible missing of device probe", any rough guess?