* Markus Armbruster (arm...@redhat.com) wrote: > "Dr. David Alan Gilbert" <dgilb...@redhat.com> writes: > > > * Markus Armbruster (arm...@redhat.com) wrote: > >> "Daniel P. Berrange" <berra...@redhat.com> writes: > [...] > >> > Realistically all the major backend subsystems (chardev, network, block, > >> > ui and migration) need to be converted to Error ** propagation, since > >> > they all ultimately call into some common code that reports Error **. > >> > >> Infrastucture generally doesn't know how it's used, which means > >> error_report() is generally wrong there. Sufficiently simple functions > >> can keep returning -errno, null, whatever, but the interesting stuff > >> needs to use Error. > >> > Very few places will end up being able to stick with -errno, or plain > >> > error_report in the long term. > >> > >> Not sure about "very few". Less than now. We'll see. > > > > I'd also prefer we got the very-few level; Migration used to be > > characterised by getting a 'load of migration failed -22' and having > > no clue in the logs to why; I've slowly fought back to be able > > to get an error from the lowest level that caused the failure. > > I want more of that, so that when someone gets a rare failure in the field > > I can see why. > > When it's about details that are only useful for debugging, logging > might be a practical alternative. No excuse for shoddy error reporting, > of course.
It's detail I want in the initial error report rather than future debug; to give a real example: qemu-system-ppc64: 9223477658187168481 != 9223477658187151905 qemu-system-ppc64: Failed to load cpu:env.insns_flags qemu-system-ppc64: error while loading state for instance 0x0 of device 'cpu' qemu-system-ppc64: load of migration failed: Invalid argument I wouldn't want to log the value loaded from each field unless I'm in the pain of really bad debugging; but when one goes wrong like this getting the value mismatch, the field name, and the device that failed is what I want in the logs. One point here is that those lines each come from a different function as we come back up out of the failure; the one at the bottom doesn't have the information on the device it's loading, just that it's loading an integer and it's not the expected value. Dave -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
