Bug 844579

Summary:	virtio-rng: 'cat' process hangs when ^C pressed when there's no input
Product:	Red Hat Enterprise Linux 6	Reporter:	Amit Shah <amit.shah>
Component:	kernel	Assignee:	Amit Shah <amit.shah>
Status:	CLOSED ERRATA	QA Contact:	Virtualization Bugs <virt-bugs>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	6.4	CC:	juzhang, mdeng, michen, qzhang, rhod, shuang, virt-maint
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	kernel-2.6.32-298.el6	Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2013-02-21 06:44:11 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Amit Shah 2012-07-31 06:16:48 UTC

Description of problem:

When the host doesn't provide the virtio-rng driver with any data, this set of commands just hangs:

# cat /dev/hwrng
^C

Instead of using wait_for_completion(), use wait_for_completion_killable() to ensure the read is killable.

For testing this, the virtio-rng device isn't yet available upstream or in a RHEL release.  I can give a qemu-kvm build to QE for testing and verification purposes, let me know when you need it.

Comment 1 Amit Shah 2012-07-31 06:21:26 UTC

Upstream commit with fix is cc8744e12936680478ce82b0f21dbaa272df1447

Comment 2 RHEL Program Management 2012-08-06 10:11:36 UTC

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

Comment 3 juzhang 2012-08-09 02:56:28 UTC

qe will verify this bug along with bz844583/844582/786407

Comment 5 Jarod Wilson 2012-08-16 15:01:01 UTC

Patch(es) available on kernel-2.6.32-298.el6

Comment 8 Qunfang Zhang 2012-12-27 05:21:08 UTC

Hi, Amit
We want to verify the virt-rng related bugs in kernel component but seems virtio-rng device is still not available in qemu-kvm official build? 
BTW, do we have a qemu-kvm bug to track it?

Comment 10 Qunfang Zhang 2012-12-28 07:00:34 UTC

Hi Amit
I tried to reproduce the issue with kernel-279 installed in guest.

Steps:
0. I'm using the upstream qemu-kvm because currently neither rhel6 nor rhel7 has virtio-rng device.

1. Boot guest with  "-device virtio-rng-pci,bus=pci.0,addr=0xa,id=rng0"

2. After guest boot up. 
(1)#cat /etc/hwrng
(2)"Ctrl+c" to kill the above command.

Result: In a rhel6.3 guest kernel (kernel-279), the command hangs for a while, about 5 to 10 seconds. But at last the command is killed. 

And then I verified this issue with a rhel6.4 guest (kernel-348). 

Result: After step 2.(2), the command could be killed immediately. 

Amit,
Is this the reproduction phenomenon in the older kernel-279?  It is not always hang, but only for some seconds.

Thanks,
Qunfang

Comment 11 Qunfang Zhang 2012-12-28 07:44:04 UTC

I think this can be verified pass with the following steps:

1. Boot guest with  "-device virtio-rng-pci,bus=pci.0,addr=0xa,id=rng0"

2. Inside guest:
#cat /dev/hwrng

3. #pm-suspend

4. Resume guest.

5. Using "Ctrl+c" to kill the command in step 2. 

Result:
In the old kernel-2.6.32-279.el6.x86_64, the command can not be killed. 
In the newer kernel-2.6.32-348.el6.x86_64, the command can be killed immediately.

So based on comment 10 and comment 11, this bug can be verified.

Comment 12 Amit Shah 2013-01-02 11:47:07 UTC

Steps in comment 10 and 11 look correct.  Thanks.

Comment 14 errata-xmlrpc 2013-02-21 06:44:11 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2013-0496.html