[libvirt] [PATCH 00/19] Rollback migration when libvirtd restarts

[Eric Blake]

On 07/07/2011 05:34 PM, Jiri Denemark wrote:
> This series is also available at
> https://gitorious.org/~jirka/libvirt/jirka-staging/commits/migration-recovery
>
> The series does several things:
> - persists current job and its phase in status xml
> - allows safe monitor commands to be run during migration/save/dump jobs
> - implements recovery when libvirtd is restarted while a job is active
> - consolidates some code and fixes bugs I found when working in the area

git bisect is pointing to this series as the cause of a regression in 
'virsh managedsave dom' triggering libvirtd core dumps if some other 
process is actively making queries on domain at the same time 
(virt-manager is a great process for fitting that bill).  I'm trying to 
further narrow down which patch introduced the regression, and see if I 
can plug the race (probably a case of not checking whether the monitor 
still exists when getting the condition for an asynchronous job, since 
the whole point of virsh [managed]save is that the domain will go away 
when the save completes, but that it is time-consuming enough that we 
want to query domain state in the meantime).

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff06d0700 (LWP 11419)]
0x00000000004b9ad8 in qemuMonitorSend (mon=0x7fffe815c060, 
msg=0x7ffff06cf380)
     at qemu/qemu_monitor.c:801
801	    while (!mon->msg->finished) {
(gdb) bt
#0  0x00000000004b9ad8 in qemuMonitorSend (mon=0x7fffe815c060,
     msg=0x7ffff06cf380) at qemu/qemu_monitor.c:801
#1  0x00000000004c77ae in qemuMonitorJSONCommandWithFd (mon=0x7fffe815c060,
     cmd=0x7fffd8000940, scm_fd=-1, reply=0x7ffff06cf480)
     at qemu/qemu_monitor_json.c:225
#2  0x00000000004c78e5 in qemuMonitorJSONCommand (mon=0x7fffe815c060,
     cmd=0x7fffd8000940, reply=0x7ffff06cf480) at 
qemu/qemu_monitor_json.c:254
#3  0x00000000004cc19c in qemuMonitorJSONGetMigrationStatus (
     mon=0x7fffe815c060, status=0x7ffff06cf580, transferred=0x7ffff06cf570,
     remaining=0x7ffff06cf568, total=0x7ffff06cf560)
     at qemu/qemu_monitor_json.c:1920
#4  0x00000000004bc1b3 in qemuMonitorGetMigrationStatus 
(mon=0x7fffe815c060,
     status=0x7ffff06cf580, transferred=0x7ffff06cf570,
     remaining=0x7ffff06cf568, total=0x7ffff06cf560) at 
qemu/qemu_monitor.c:1532
#5  0x00000000004b201b in qemuMigrationUpdateJobStatus 
(driver=0x7fffe80089f0,
     vm=0x7fffe8015cd0, job=0x5427b6 "domain save job")
     at qemu/qemu_migration.c:765
#6  0x00000000004b2383 in qemuMigrationWaitForCompletion (
     driver=0x7fffe80089f0, vm=0x7fffe8015cd0) at qemu/qemu_migration.c:846
#7  0x00000000004b7806 in qemuMigrationToFile (driver=0x7fffe80089f0,
     vm=0x7fffe8015cd0, fd=27, offset=4096,
     path=0x7fffd8000990 "/var/lib/libvirt/qemu/save/fedora_12.save",
     compressor=0x0, is_reg=true, bypassSecurityDriver=true)
     at qemu/qemu_migration.c:2766
#8  0x000000000046a90d in qemuDomainSaveInternal (driver=0x7fffe80089f0,
     dom=0x7fffd8000ad0, vm=0x7fffe8015cd0,
     path=0x7fffd8000990 "/var/lib/libvirt/qemu/save/fedora_12.save",
     compressed=0, bypass_cache=false) at qemu/qemu_driver.c:2386


-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org