Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757389Ab3J1Rdd (ORCPT ); Mon, 28 Oct 2013 13:33:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57862 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757353Ab3J1Rd3 (ORCPT ); Mon, 28 Oct 2013 13:33:29 -0400 Date: Mon, 28 Oct 2013 18:30:56 +0100 From: Veaceslav Falico To: Bjorn Helgaas Cc: Greg Kroah-Hartman , Linus Torvalds , Thomas Gleixner , Yinghai Lu , Knut Petersen , Ingo Molnar , Paul McKenney , =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , linux-kernel , "linux-pci@vger.kernel.org" Subject: Re: [BUG 3.12.rc4] Oops: unable to handle kernel paging request during shutdown Message-ID: <20131028173056.GF11209@redhat.com> References: <525BD08C.2080101@t-online.de> <20131027212407.GA17439@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2443 Lines: 62 On Mon, Oct 28, 2013 at 11:23:41AM -0600, Bjorn Helgaas wrote: >[+cc Veaceslav] > >On Sun, Oct 27, 2013 at 3:24 PM, Greg Kroah-Hartman > wrote: >> On Sun, Oct 27, 2013 at 09:13:29PM +0000, Linus Torvalds wrote: >>> .. and one more case of freeing a delayed work object (likely a kobject again): >>> >>> This time it looks like it's in the PCI layer, freeing the msi irq information. >>> >>> It looks like that code simply does >>> >>> kobject_del(&entry->kobj); >>> kobject_put(&entry->kobj); >>> list_del(&entry->list); >>> kfree(entry); >>> >>> and the problem is that the "entry->kobj" may have *other* references >>> to it, thanks to people accessing it through /sys, so despite doing a >>> kojbect_del/kobject_put(), it's not at all ok to then do a "kfree()" >>> on it. The embedded kobj might still be in use. >>> >>> Afaik, that code should do the kfree() on the kobject in the _release_ >>> method, not synchronously like that. >>> >>> We already have a msi_kobj_release(), I'm wondering why that doesn't >>> do the kfree(). >>> >>> Bjorn? Yinghai? Greg, comments about that msi kobj usage? >> >> Ick, it really should be doing a kfree() in the release only. Bjorn has >> had a bunch of changes in this area recently, perhaps they are in >> linux-next waiting for 3.13, and I've talked to him about getting rid of >> all of the kobjects for msi files, as I don't think it's needed at all. > >IIRC, you said you might take a look at converting this to attributes >on the train back home, so I haven't looked into it myself :) > >> Bjorn, don't you have a fix for this problem already done somewhere? > >Yep, this is clearly wrong, and Veaceslav has a patch that moves the >kfree() to the release function. I've been waiting for a consolidated >repost of all his MSI-related fixes, but maybe he's been waiting for >*me*. https://lkml.org/lkml/2013/10/9/170 My patchset is ready to be applied, in its v2 state. Except that the bits with kobject_del() (theoretical race) - which are done in your patch "kobject: remove kset from sysfs immediately in kset_unregister()", though I didn't see it accepted. Should I re-send the patchset? > >Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/