Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932153Ab3J1Rfc (ORCPT ); Mon, 28 Oct 2013 13:35:32 -0400 Received: from mail-ie0-f178.google.com ([209.85.223.178]:61428 "EHLO mail-ie0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756848Ab3J1Rfa (ORCPT ); Mon, 28 Oct 2013 13:35:30 -0400 MIME-Version: 1.0 In-Reply-To: <20131028173056.GF11209@redhat.com> References: <525BD08C.2080101@t-online.de> <20131027212407.GA17439@kroah.com> <20131028173056.GF11209@redhat.com> From: Bjorn Helgaas Date: Mon, 28 Oct 2013 11:35:09 -0600 Message-ID: Subject: Re: [BUG 3.12.rc4] Oops: unable to handle kernel paging request during shutdown To: Veaceslav Falico 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" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2769 Lines: 75 On Mon, Oct 28, 2013 at 11:30 AM, Veaceslav Falico wrote: > 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? Can you please repost it? That will be easier for me than digging individual messages out of the archives. Thanks, and sorry for my confusion. 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/