Fixed upstream by:
commit f0f9eed843edf1339bb7b078d98e985b11f5f240
Author:     Sam Bobroff <sam.bobroff.com>
AuthorDate: 2014-08-12 12:54:42 +1000
Commit:     Ján Tomko <jtomko>
CommitDate: 2014-08-14 12:12:42 +0200

    qemu: Tidy up job handling during live migration
    
    During a QEMU live migration several warning messages about job
    handling could be written to syslog on the destination host:
    
    "entering monitor without asking for a nested job is dangerous"
    
    The messages are written because the job handling during migration
    uses hard coded asyncJob values in several places that are incorrect.
    
    This patch passes the required asyncJob value around and prevents
    the warnings as well as any issues that the warnings may be referring
    to.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1130089
    
    Signed-off-by: Sam Bobroff <sam.bobroff.com>
    Signed-off-by: Ján Tomko <jtomko>

git describe: v1.2.7-58-gf0f9eed

Verify this issue with build libvirt-1.2.8-1.el7.x86_64:

Verify steps:
1. Set up migration env with nfs


2. On source host, prepare a running guest (rhel6-guest), run following
command:

[root@rhel7-a /]# virsh migrate --live rhel6-guest qemu+ssh://destEnv/system --verbose

3. Before migration done, running following commands on destination host:
[root@rhel7-b /]# while true; do virsh destroy rhel6-guest ;  done


Actual Result:
1. Following error will show on source host:
Migration: [  75 %]error: operation failed: migration job: unexpectedly failed

2. Check libvirtd status both on source and destination hosts with following command:
#service libvirtd status

Both are good, not deadlock occurs.


3. Check libvirtd.log on destination host:
No warning about "entering monitor without asking for a nested job is dangerous" are found.

Reproduce this issue with build libvirt-1.1.1-29.el7_0.1 + following patch:

---
 src/qemu/qemu_process.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 5b598be..91e9b55 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -4290,6 +4290,8 @@ int qemuProcessStart(virConnectPtr conn,
         goto cleanup;
     }
     qemuDomainObjEnterMonitor(driver, vm);
+    VIR_ERROR("Sleeping for three seconds...");
+    sleep(3);
     if (vm->def->memballoon && vm->def->memballoon->period)
         qemuMonitorSetMemoryStatsPeriod(priv->mon, vm->def->memballoon->period);
     if (qemuMonitorSetBalloon(priv->mon, cur_balloon) < 0) {
-- 



Reproduce steps:
1. With above patch, create rpms for build libvirt-1.1.1-29.el7_0.1, and install all these rpms on both source and destination host.

2. Open log feature for libvirtd in /etc/libvirt/libvirtd.conf on destination host with:
# grep ^log /etc/libvirt/libvirtd.conf 
log_level = 1
log_outputs="1:file:/var/log/libvirt/libvirtd.log"


3. Restart the libvirtd service on destination host.

4. Setup a migration environment with nfs

5. Prepare a running guest named "rhel6" on source host

6. On Destination host, run following command:
# while true; do grep "Sleeping for three seconds"  /var/log/libvirt/libvirtd.log && sleep 1 && virsh destroy rhel6 ;  done

7. Migrate the guest named "rhel6" from source to destination:
#virsh migrate --live rhel6 qemu+ssh://destinationHost/system --verbose

Actual Result:
On Destination host:
# while true; do grep "Sleeping for three seconds"  /var/log/libvirt/libvirtd.log && virsh destroy rhel6 ;  done
2014-10-09 06:47:18.293+0000: 2707: error : qemuProcessStart:4219 : Sleeping for three seconds...

error: Failed to destroy domain rhel6
error: internal error: received hangup / error event on socket

Check libvirtd service:
The libvirtd service deadlock, and will hang up when issue command "virsh list"







Verify this issue with build libvirt-1.2.8-4.el7.x86_64 + following patch:

---
 src/qemu/qemu_process.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 9294619..a57d857 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -5200,6 +5200,8 @@ int qemuProcessAttach(virConnectPtr conn ATTRIBUTE_UNUSED,
                              VIR_DOMAIN_RUNNING_UNPAUSED);
         if (vm->def->memballoon && vm->def->memballoon->period) {
             qemuDomainObjEnterMonitor(driver, vm);
+            VIR_ERROR("Sleeping for three seconds...");
+            sleep(3); 
             qemuMonitorSetMemoryStatsPeriod(priv->mon,
                                             vm->def->memballoon->period);
             qemuDomainObjExitMonitor(driver, vm);
-- 


Verify Steps:
1. With above patch, create rpms for build libvirt-1.2.8-4.el7.x86_64, and install all these rpms on both source and destination host.

2. Open log feature for libvirtd in /etc/libvirt/libvirtd.conf on destination host with:
# grep ^log /etc/libvirt/libvirtd.conf 
log_level = 1
log_outputs="1:file:/var/log/libvirt/libvirtd.log"


3. Restart the libvirtd service on destination host.

4. Setup a migration environment with nfs

5. Prepare a running guest named "rhel6" on source host

6. On Destination host, run following command:
# while true; do grep "Sleeping for three seconds"  /var/log/libvirt/libvirtd.log && sleep 1 && virsh destroy rhel6 ;  done

7. Migrate the guest named "rhel6" from source to destination:
#virsh migrate --live rhel6 qemu+ssh://destinationHost/system --verbose

Actual Result:
On Destination host:
# while true; do grep "Sleeping for three seconds"  /var/log/libvirt/libvirtd.log && virsh destroy rhel6 ;  done


Check libvirtd service:
The libvirtd service works well.

I can reproduce the bug follow the reproducer in comment 0, the reproduce steps as following

1.Recompile the libvirt packet with the following patch on the target host

---
 src/qemu/qemu_process.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 9294619..a57d857 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -5200,6 +5200,8 @@ int qemuProcessAttach(virConnectPtr conn ATTRIBUTE_UNUSED,
                              VIR_DOMAIN_RUNNING_UNPAUSED);
         if (vm->def->memballoon && vm->def->memballoon->period) {
             qemuDomainObjEnterMonitor(driver, vm);
+            VIR_ERROR("Sleeping for three seconds...");
+            sleep(3); 
             qemuMonitorSetMemoryStatsPeriod(priv->mon,
                                             vm->def->memballoon->period);
             qemuDomainObjExitMonitor(driver, vm);
-- 

2.setting log_level and log_output in /etc/libvirt/libvirtd.conf on destination host with:
# grep ^log /etc/libvirt/libvirtd.conf 
log_level = 1
log_outputs="1:file:/var/log/libvirt/libvirtd.log"

#service libvirtd restart

3.Prepare the nfs migration env in both source and target host

4.Run the following command in the target host
# while true; do grep "Sleeping for three seconds"  /var/log/libvirt/libvirtd.log && sleep 1 && virsh destroy rhel7.0 ;  done

5.Migrate the guest from the source to the target and run the virsh list command in the target host, we could see libvirtd hang there

# while true; do grep "Sleeping for three seconds"  /var/log/libvirt/libvirtd.log && sleep 1 && virsh destroy rhel7.0 ;  done
2014-12-09 05:46:13.921+0000: 27190: error : qemuProcessStart:4092 : Sleeping for three seconds...

# virsh list --all
^C

Verify this bug with libvirt-1.2.8-10.el7.x86_64 

steps 
1.compile the libvirtd code with the following patch on the target host

int qemuProcessStart(virConnectPtr conn,
                     virQEMUDriverPtr driver,
--
if (qemuDomainObjEnterMonitorAsync(driver, vm, asyncJob) < 0)
        goto cleanup;
        VIR_ERROR("Sleeping for three seconds...");
        sleep(3);
    if (vm->def->memballoon && vm->def->memballoon->period)
        qemuMonitorSetMemoryStatsPeriod(priv->mon, vm->def->memballoon->period);
    if (qemuMonitorSetBalloon(priv->mon, cur_balloon) < 0) {
        qemuDomainObjExitMonitor(driver, vm);
        goto cleanup;
    }


2.Setting log_level and log_output in /etc/libvirt/libvirtd.conf on destination host with:
<target># grep ^log /etc/libvirt/libvirtd.conf 
log_level = 1
log_outputs="1:file:/var/log/libvirt/libvirtd.log"

<target>#service libvirtd restart

3.Prepare the nfs migration env in both source and target host

4.Run the following command in the target host
<target1># while true; do grep "Sleeping for three seconds"  /var/log/libvirt/libvirtd.log && sleep 1 && virsh destroy rhel7.0 ;  done

5.Migrate the guest from the source to the target and run the virsh list command in the target host, the guest will fail to migrate in the source host and libvirtd on target host didn't show deadlock.
<source> # virsh migrate --live rhel7.0 qemu+ssh://$target_ip/system --verbose 
root.4.165's password: 
error: internal error: early end of file from monitor: possible problem:
qemu: terminating on signal 15 from pid 21314


<target1> # while true; do grep "Sleeping for three seconds"  /var/log/libvirt/libvirtd.log && sleep 1 && virsh destroy rhel7.0 ;  done
2014-12-09 09:25:58.340+0000: 21357: error : qemuProcessStart:4782 : Sleeping for three seconds...
error: Failed to destroy domain rhel7.0
error: Requested operation is not valid: domain is not running

2014-12-09 09:25:58.340+0000: 21357: error : qemuProcessStart:4782 : Sleeping for three seconds...
error: failed to get domain 'rhel7.0'
error: Domain not found: no domain with matching name 'rhel7.0'

<target2># virsh list --all
 Id    Name                           State
----------------------------------------------------


5.cancel the script in target1 , then re-migrate the guest rhel7.0 from the source to the target , the guest could be migrated successfully

According to the upper steps , mark this bug verifed

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.

https://rhn.redhat.com/errata/RHSA-2015-0323.html