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.