Bug 438439

Summary:	xenbus driver leaks sysfs device entries for PVFB
Product:	Red Hat Enterprise Linux 5	Reporter:	Daniel Berrangé <berrange>
Component:	kernel-xen	Assignee:	Markus Armbruster <armbru>
Status:	CLOSED DUPLICATE	QA Contact:	Martin Jenner <mjenner>
Severity:	high	Docs Contact:
Priority:	high
Version:	5.2	CC:	clalance, minovotn, syeghiay, xen-maint
Target Milestone:	rc
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2009-04-10 09:44:53 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	448753, 492570

Description Daniel Berrangé 2008-03-20 21:19:22 UTC

Description of problem:
Create a paravirt guest with the framebuffer configured, and then destroy it
again. The /sys/class/xen-backend/devices/ directory will contain 2 nods for the
VFB and VKBD devices. These nodes never appear to go away.

Version-Release number of selected component (if applicable):
kernel-2.6.18-84.el5

How reproducible:
Always

Steps to Reproduce:
1. Edit /etc/xen/GUEST and add 
2.vfb = [ "type=vnc,vncunused=1"]
3. virsh start GUEST
4. Let it boot
5. virsh destroy GUEST
6. ls /sys/bus/xen-backend/devices/

Actual results:
Two directories are still present:

vfb-DOMID-0
vkbd-DOMID-0

Expected results:
No directories are left behind

Additional info:

Comment 1 Daniel Berrangé 2008-03-20 21:22:22 UTC

The problem appears to be with the delegation of responsibility between the
xenbus module, and the backend specific modules.

The sysfs node is added when the xenbus_probe_node() method in the xenbus module
calls device_register().


The corresponding call for device_unregister() though is in th backend specific
modules. eg, the frontend_changed() method in  the blkback module.

There does not appear to be any generic fallback code in xenbus to call
device_unregister() for device's whose backend lives in userspace such as VFB.

Comment 3 RHEL Program Management 2008-07-24 16:11:04 UTC

This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux maintenance release.  Product Management has requested
further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed
products.  This request is not yet committed for inclusion in an Update
release.

Comment 6 Michal Novotny 2009-04-08 15:17:43 UTC

In fact, when you do `xenstore-rm /local/domain/0/backend/{deviceClass}/{domid}` it automatically deletes those files in sysfs. I am working investigating it now...

Comment 7 Michal Novotny 2009-04-09 10:26:39 UTC

I seems to be connected to BZ #439182. I've created and done workaround/patch and posted it to this BZ.

Comment 8 Chris Lalancette 2009-04-10 09:44:53 UTC

I'm going to close this as a dup of 439182, then.  If it turns out to be different, we can re-open.

Chris Lalancette

*** This bug has been marked as a duplicate of bug 439182 ***