Re: [libvirt] PATCH: Fix infinite loop when QEMU quits at startup

"Daniel P. Berrange" <berrange(a)redhat.com&gt; wrote: > The recent refactoring of the QEMU startup process now reads the monitor > TTY from the logfile. Unfortunately in this refactoring we lost the check > for the 'ret == 0' scenario in the read() return value. So if QEMU quits > at startup, eg due to missing disk image, we loop forever on read() == 0 > because we hit end-of-file and QEMU has quit. > > This patch adds back handling for this scenario, and takes care to > propagate the contents of the log to the user as an error message > > # start demo > libvir: QEMU error : internal error unable to start guest: qemu: could > not open disk image /home/berrange/Fedora-9-i686-Live.iso > error: Failed to start domain demo > > In addition, there were a couple of other bugs > > > - a memory leak where we set the 'monitorpath' variable, even > though we'd just set it moments before. > > - a missing check for whether the driver VNC password was present > when initializing passwords at VM startupo > > - missing initialization of the monitor_watch field, and missing > checking for whether the watch was set before removing it. > > - a gratuitous LOG_INFO when shutting down any VM, which could > just be LOG_DEBUG. FYI, I reproduced the infloop with the following: cat <<\EOF > d.xml <domain type='qemu'> <name>D</name> <uuid>c7a5fdbd-cdaf-9455-926a-d65c16db1809</uuid> <memory>219200</memory> <currentMemory>219200</currentMemory> <vcpu>2</vcpu> <os> <type arch='i686' machine='pc'>hvm</type> <boot dev='cdrom'/> </os> <devices> <emulator>/usr/bin/qemu-system-x86_64</emulator> <disk type='file' device='cdrom'> <source file='no-such-file'/> <target dev='hdc'/> <readonly/> </disk> <disk type='file' device='disk'> <source file='no-such-file'/> <target dev='hda'/> </disk> <graphics type='vnc' port='-1'/> </devices> </domain> EOF Before, this use of virsh would hang: qemud/libvirtd & src/virsh -c qemu:///session "define d.xml; start D" Now, it fails with a diagnostic, as you'd expect.

Somehow, while testing this, I got numerous segfaults from libvirtd (due to dereferencing NULL doms->objs[i]->def, but those should never be NULL), yet when I went to set up a reproducer, it stopped happening altogether.