From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg KH Subject: Re: [PATCH v2 1/2] sysfs: handle 'parent deleted before child added' Date: Fri, 6 Apr 2012 14:17:11 -0700 Message-ID: <20120406211711.GA12075@kroah.com> References: <20120406203619.22624.69445.stgit@dwillia2-linux.jf.intel.com> <20120406204514.GA20237@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail-pz0-f52.google.com ([209.85.210.52]:52852 "EHLO mail-pz0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757807Ab2DFVRP (ORCPT ); Fri, 6 Apr 2012 17:17:15 -0400 Received: by dake40 with SMTP id e40so3119840dak.11 for ; Fri, 06 Apr 2012 14:17:15 -0700 (PDT) Content-Disposition: inline In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: "Williams, Dan J" Cc: James Bottomley , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org On Fri, Apr 06, 2012 at 02:06:50PM -0700, Williams, Dan J wrote: > On Fri, Apr 6, 2012 at 1:45 PM, Greg KH = wrote: > > On Fri, Apr 06, 2012 at 01:41:06PM -0700, Dan Williams wrote: > >> In scsi at least two cases of the parent device being deleted befo= re the > >> child is added have been observed. > >> > >> 1/ scsi is performing async scans and the device is removed prior = to the > >> =A0 =A0async can thread running (can happen with an in-opportune /= unlikely > >> =A0 =A0unplug during initial scan). > > > > That sounds like a bug in the scsi code, doesn't it? > > > >> 2/ libsas discovery event running after the parent port has been t= orn > >> =A0 =A0down (this is a bug in libsas). > > > > Is this fixed somewhere? >=20 > Yes, these two issues have pending fixes that are posted to linux-scs= i: >=20 > http://marc.info/?l=3Dlinux-scsi&m=3D133239707903443&w=3D2 > http://marc.info/?l=3Dlinux-scsi&m=3D133239709603452&w=3D2 >=20 > > I don't want to paper over bugs like this by changing the sysfs cor= e. > > We went through this a lot years ago when scsi changed to use the d= river > > core, and I thought we had fixed all of these types of errors prope= rly. >=20 > Hotplug lifetime rules are still transport specific. So in this case > scsi-core is innocent these are bugs from libsas and > scsi_transport_sas. Ok, thanks for the explaination. > > So, any chance to fix these properly as well? >=20 > This patch doesn't really paper over anything. It turns a NULL > pointer crash into an explicit warning from kobject_add_internal. Fo= r > the libsas/scsi case this device_add() failure is still fatal. > Regardless of whether sysfs changes the above two fixes are still > required. >=20 > Since the -EEXIST case is just a KERN_ERR and not a BUG_ON I figured > it was worthwhile to post a patch to do the same for this 'parent > deleted' case. But if crashing is the expectation then this patch ca= n > be dropped. No, crashing is not the expectation :) But, without that crash, would the above fixes ever have been noticed and fixed? The device_add() most likely would have quietly failed and no one would have been the wiser. Or would something else have caused this to be an obvious problem? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758165Ab2DFVRR (ORCPT ); Fri, 6 Apr 2012 17:17:17 -0400 Received: from mail-pz0-f52.google.com ([209.85.210.52]:41463 "EHLO mail-pz0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758098Ab2DFVRP (ORCPT ); Fri, 6 Apr 2012 17:17:15 -0400 Date: Fri, 6 Apr 2012 14:17:11 -0700 From: Greg KH To: "Williams, Dan J" Cc: James Bottomley , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Subject: Re: [PATCH v2 1/2] sysfs: handle 'parent deleted before child added' Message-ID: <20120406211711.GA12075@kroah.com> References: <20120406203619.22624.69445.stgit@dwillia2-linux.jf.intel.com> <20120406204514.GA20237@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 06, 2012 at 02:06:50PM -0700, Williams, Dan J wrote: > On Fri, Apr 6, 2012 at 1:45 PM, Greg KH wrote: > > On Fri, Apr 06, 2012 at 01:41:06PM -0700, Dan Williams wrote: > >> In scsi at least two cases of the parent device being deleted before the > >> child is added have been observed. > >> > >> 1/ scsi is performing async scans and the device is removed prior to the > >>    async can thread running (can happen with an in-opportune / unlikely > >>    unplug during initial scan). > > > > That sounds like a bug in the scsi code, doesn't it? > > > >> 2/ libsas discovery event running after the parent port has been torn > >>    down (this is a bug in libsas). > > > > Is this fixed somewhere? > > Yes, these two issues have pending fixes that are posted to linux-scsi: > > http://marc.info/?l=linux-scsi&m=133239707903443&w=2 > http://marc.info/?l=linux-scsi&m=133239709603452&w=2 > > > I don't want to paper over bugs like this by changing the sysfs core. > > We went through this a lot years ago when scsi changed to use the driver > > core, and I thought we had fixed all of these types of errors properly. > > Hotplug lifetime rules are still transport specific. So in this case > scsi-core is innocent these are bugs from libsas and > scsi_transport_sas. Ok, thanks for the explaination. > > So, any chance to fix these properly as well? > > This patch doesn't really paper over anything. It turns a NULL > pointer crash into an explicit warning from kobject_add_internal. For > the libsas/scsi case this device_add() failure is still fatal. > Regardless of whether sysfs changes the above two fixes are still > required. > > Since the -EEXIST case is just a KERN_ERR and not a BUG_ON I figured > it was worthwhile to post a patch to do the same for this 'parent > deleted' case. But if crashing is the expectation then this patch can > be dropped. No, crashing is not the expectation :) But, without that crash, would the above fixes ever have been noticed and fixed? The device_add() most likely would have quietly failed and no one would have been the wiser. Or would something else have caused this to be an obvious problem? thanks, greg k-h