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Bug 1065225

Summary:	QMP socket breaks on unexpected close
Product:	Red Hat Enterprise Linux 7	Reporter:	Amit Shah <amit.shah>
Component:	qemu-kvm	Assignee:	Amit Shah <amit.shah>
Status:	CLOSED CURRENTRELEASE	QA Contact:	Virtualization Bugs <virt-bugs>
Severity:	urgent	Docs Contact:
Priority:	urgent
Version:	7.0	CC:	acathrow, amit.shah, bsarathy, chayang, cloud, hhuang, juzhang, konishchev, mazhang, mkenneth, qzhang, sluo, ukar, virt-maint
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	qemu-kvm-1.5.3-48.el7	Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:	1060024	Environment:
Last Closed:	2014-06-13 12:42:55 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:
Bug Depends On:	1060024
Bug Blocks:

Description Amit Shah 2014-02-14 07:23:07 UTC

RHEL7 clone.  QE, please try to reproduce using the script in the original bug.

+++ This bug was initially created as a clone of Bug #1060024 +++

QMP socket breaking script

Description of problem:

If you connect to QMP socket and immediately close it there is a big change to break QMP socket and get hung QEMU process consuming CPU on 100%. 


Version-Release number of selected component:

qemu-kvm-0.12.1.2-2.415.el6_5.3.x86_64


Steps to Reproduce:

1. Run QEMU:
   # /usr/libexec/qemu-kvm -qmp unix:/tmp/qmp,server,nowait

2. Run the attached script (specify path to qemu-kvm sources to include provided example of Python qmp module):
   # python break_qmp.py PATH/TO/QEMU/SOURCES /tmp/qmp 

You will get the following output (after one or several connects using socket you will hand on connection to QMP socket):
> Connecting to QMP...
> OK
> Connecting using socket...
> OK
> Connecting to QMP...

QEMU will burn the CPU.


Additional info:

qemu-kvm-0.12.1.2-2.355.el6_4.9:2.x86_64 doesn't have this bug.

--- Additional comment from Amit Shah on 2014-02-14 12:46:08 IST ---

We need to backport the following commit from upstream.  I've confirmed it fixes the problem.

commit 056f49ff2cf645dc484956b00b65a3aa18a1a9a3
Author: Stratos Psomadakis <psomas>
Date:   Mon Jan 27 12:30:15 2014 +0200

    monitor: Cleanup mon->outbuf on write error
    
    In case monitor_flush() fails to write the contents of mon->outbuf to
    the output device, mon->outbuf is not cleaned up properly. Check the
    return code of the qemu_chr_fe_write() function and cleanup the outbuf
    if it fails.
    
    References: http://lists.nongnu.org/archive/html/qemu-devel/2014-01/msg02890.html

Comment 1 Qunfang Zhang 2014-02-14 08:28:26 UTC

Hi, Amit

On rhel7 host (qemu-kvm-1.5.3-47.el7.x86_64), the python script shows:
# python break_qmp.py  qemu-kvm/ /tmp/qmp 
Connecting to QMP...
OK
Connecting using socket...
OK
Connecting to QMP...
Traceback (most recent call last):
  File "break_qmp.py", line 13, in <module>
    c.connect()
  File "qemu-kvm/QMP/qmp.py", line 76, in connect
    raise QMPCapabilitiesError
qmp.QMPCapabilitiesError

But it works on rhel6 bug 1060024. Could you give a help on the above issue? 


Thanks,
Qunfang

Comment 3 Amit Shah 2014-02-14 08:32:32 UTC

(In reply to Qunfang Zhang from comment #1)
> Hi, Amit
> 
> On rhel7 host (qemu-kvm-1.5.3-47.el7.x86_64), the python script shows:
> # python break_qmp.py  qemu-kvm/ /tmp/qmp 
> Connecting to QMP...
> OK
> Connecting using socket...
> OK
> Connecting to QMP...
> Traceback (most recent call last):
>   File "break_qmp.py", line 13, in <module>
>     c.connect()
>   File "qemu-kvm/QMP/qmp.py", line 76, in connect
>     raise QMPCapabilitiesError
> qmp.QMPCapabilitiesError
> 
> But it works on rhel6 bug 1060024. Could you give a help on the above issue? 

The expected result is thta this traceback doesn't happen, and the connecting...OK sequences keep happening in a loop.  Please try the brew build.

For RHEL6, the python script doesn't quit, but instead just freezes, and if you see 'top' output, qemu uses 100% cpu.  With the fix, RHEL6 too will just continue connecting and disconnecting in a loop.

Comment 4 Sibiao Luo 2014-02-14 08:38:06 UTC

(In reply to Amit Shah from comment #3)
> (In reply to Qunfang Zhang from comment #1)
> > Hi, Amit
> > 
> > On rhel7 host (qemu-kvm-1.5.3-47.el7.x86_64), the python script shows:
> > # python break_qmp.py  qemu-kvm/ /tmp/qmp 
> > Connecting to QMP...
> > OK
> > Connecting using socket...
> > OK
> > Connecting to QMP...
> > Traceback (most recent call last):
> >   File "break_qmp.py", line 13, in <module>
> >     c.connect()
> >   File "qemu-kvm/QMP/qmp.py", line 76, in connect
> >     raise QMPCapabilitiesError
> > qmp.QMPCapabilitiesError
> > 
> > But it works on rhel6 bug 1060024. Could you give a help on the above issue? 
> 
> The expected result is thta this traceback doesn't happen, and the
> connecting...OK sequences keep happening in a loop.  Please try the brew
> build.
> 
> For RHEL6, the python script doesn't quit, but instead just freezes, and if
> you see 'top' output, qemu uses 100% cpu.  With the fix, RHEL6 too will just
> continue connecting and disconnecting in a loop.

Tried your build also meet the same problem as comment #3.
# uname -r && rpm -q qemu-kvm
3.10.0-86.el7.x86_64
qemu-kvm-1.5.3-45.el7.bz1065225.x86_64

# python break_qmp.py /home/qemu-kvm /tmp/qmp 
Connecting to QMP...
OK
Connecting using socket...
OK
Connecting to QMP...
Traceback (most recent call last):
  File "break_qmp.py", line 13, in <module>
    c.connect()
  File "/home/qemu-kvm/QMP/qmp.py", line 87, in connect
    return self.__negotiate_capabilities()
  File "/home/qemu-kvm/QMP/qmp.py", line 59, in __negotiate_capabilities
    raise QMPCapabilitiesError
qmp.QMPCapabilitiesError

Comment 5 Amit Shah 2014-02-14 09:28:41 UTC

(In reply to Sibiao Luo from comment #4)
> Tried your build also meet the same problem as comment #3.

Can you try multiple times?  Do you get the same result each time?

Comment 6 Sibiao Luo 2014-02-14 09:32:23 UTC

(In reply to Amit Shah from comment #5)
> (In reply to Sibiao Luo from comment #4)
> > Tried your build also meet the same problem as comment #3.
> 
> Can you try multiple times?  Do you get the same result each time?
sure, each time can hit it.

Comment 7 Amit Shah 2014-02-14 10:17:04 UTC

Strange.  In my testing, with the patch, I don't see any problems and the script continues to run, whereas without the patch, the script aborts quickly.

Comment 8 Miroslav Rezanina 2014-02-17 09:38:49 UTC

Fix included in qemu-kvm-1.5.3-48.el7

Comment 10 mazhang 2014-02-25 03:12:35 UTC

Reproduce this bug with qemu-kvm-1.5.3-41.el7.x86_64.

[root@m1 ~]# python break_qmp.py /root/source/qemu-kvm /tmp/qmp 
Connecting to QMP...
OK
Connecting using socket...
OK
Connecting to QMP...
Traceback (most recent call last):
  File "break_qmp.py", line 13, in <module>
    c.connect()
  File "/root/source/qemu-kvm/QMP/qmp.py", line 87, in connect
    return self.__negotiate_capabilities()
  File "/root/source/qemu-kvm/QMP/qmp.py", line 59, in __negotiate_capabilities
    raise QMPCapabilitiesError
qmp.QMPCapabilitiesError


Update qemu-kvm and re-test this bug.

Host:
qemu-kvm-debuginfo-1.5.3-49.el7.x86_64
qemu-img-1.5.3-49.el7.x86_64
libvirt-daemon-driver-qemu-1.1.1-22.el7.x86_64
qemu-kvm-common-1.5.3-49.el7.x86_64
qemu-kvm-tools-1.5.3-49.el7.x86_64
qemu-kvm-1.5.3-49.el7.x86_64

Steps:
# /usr/libexec/qemu-kvm -qmp unix:/tmp/qmp,server,nowait
VNC server running on `::1:5900'

Result:
1. Continue output following:
Connecting using socket...
OK
Connecting to QMP...
OK
Connecting using socket...
OK
Connecting to QMP...
OK
Connecting using socket...
OK
Connecting to QMP...
OK
Connecting using socket...
OK

2. qemu-kvm uses 70~80% cpu.

This bug has been fixed.

Comment 12 Ludek Smid 2014-06-13 12:42:55 UTC

This request was resolved in Red Hat Enterprise Linux 7.0.

Contact your manager or support representative in case you have further questions about the request.