On Thu, Jul 30, 2020 at 11:24:51AM -0500, Eric Blake wrote: > On 7/30/20 10:59 AM, Daniel P. Berrangé wrote: > > > > Well, I suspect that management-layer code currently has > > > gone for "assume we're always running on Linux" and was > > > written by people who knew they were getting a Linux tid... > > > > Yes, on the libvirt side, the functionality that relies on thread_is is > > only compiled on Linux. If someone wants to use it on other OS, they'll > > have to provide an impl using their platforms equivalent of > > sched_setaffinity and friends since none of this stuff is standardized > > across OS. > > > > > > > > The PID is quite unlikely to be "an OS-specific identifier of the > > > > current thread". Shouldn't we fail instead of lie when we don't know > > > > how to compute the truth? > > > > > > Yeah, I think the default codepath is pretty bogus too. Should > > > the QMP functions have a mechanism for saying "we don't know > > > a thread-id on this platform" ? > > > > Thread_id should be optional and thus not filled in if we > > can't provide a sensible value. Unfortunately we made it > > mandatory in QMP. > > Normally, converting a mandatory output value to optional is a > back-compatibility risk (we could break apps that depended on it being > present). But if the only apps that depended on it being present are > compiled on Linux, where the member will actually be present, I think that > changing the schema to make it optional for non-Linux platforms won't be a > back-compatibility nightmare (but we will have to be careful in our > documentation).
FWIW, libvirt treats it as mandatory for query-iothreads, but optional for query-cpus because it was missing in some older QEMU versions entirely. Libvirt explicitly only supports macOS, Linux and FreeBSD, so if those platforms all report a value, libvirt won't care if you make it optional and omit it for other platforms. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
