Re: [libvirt] [PATCH v2] qemu_migration: Avoid crashing if domain dies too quickly
-----Original Message-----
From: Michal Privoznik [mailto:mprivozn@redhat.com]
Sent: Friday, October 18, 2013 2:37 PM
To: Wangyufei (A)
Cc: libvir-list(a)redhat.com; Wangrui (K)
Subject: Re: [libvirt] [PATCH v2] qemu_migration: Avoid crashing if domain
dies too quickly
On 18.10.2013 08:22, Wangyufei (A) wrote:
> I'm sorry. I didn't get what you mean.
>
> In virQEMUCapsInitQMP
>
> if (!(xmlopt = virDomainXMLOptionNew(NULL, NULL, NULL)) ||
> !(vm = virDomainObjNew(xmlopt)))
> goto cleanup;
>
> vm->pid = pid; //Apparently vm is not NULL here.
>
> if (!(mon = qemuMonitorOpen(vm, &config, true, &callbacks, NULL)))
{ //If qemuMonitorOpen returns NULL here, but not do mon->vm =
virObjectRef(vm); in qemuMonitorOpenInternal.
> ret = 0;
> goto cleanup; // We go to cleanup here.
> }
>
> virObjectLock(mon);
>
> if (virQEMUCapsInitQMPMonitor(qemuCaps, mon) < 0)
> goto cleanup;
>
> ret = 0;
>
> cleanup:
> if (mon)
> virObjectUnlock(mon);
> qemuMonitorClose(mon);
> virCommandAbort(cmd);
> virCommandFree(cmd);
> VIR_FREE(monarg);
> VIR_FREE(monpath);
> virObjectUnref(vm); //vm is not NULL here, and we'll do
something about vm->refs, right?
Yes. In fact we dispose @vm as we are the only one holding reference to
it and we don't longer need it. If qemuMonitorOpenInternal would do
virObjectRef(vm), then vm->refs = 2 before executing this line. After
If qemuMonitorOpenInternal did not do virObjectRef(vm) and return NULL before it, then
vm->refs = 1 before executing this line. Right?
Now we do virObjectUnref(vm), vm will be disposed here, and that's we expected. Fine,
I've got you. Thanks a lot.
the execution, the refs is decremented to 1 as @mon is the only one
holding reference to @vm.
> virObjectUnref(xmlopt);