On Fri, 22 Feb 2019 at 21:48, Roman Bolshakov <r.bolsha...@yadro.com> wrote: > > On Fri, Feb 22, 2019 at 03:41:05PM +0000, Peter Maydell wrote: > > On Fri, 22 Feb 2019 at 15:19, Roman Bolshakov <r.bolsha...@yadro.com> wrote: > > > > > > On Thu, Feb 14, 2019 at 10:28:10AM +0000, Peter Maydell wrote: > > > > The Cocoa UI should run on the main thread; this is enforced > > > > in OSX Mojave. In order to be able to run on the main thread, > > > > we need to make sure we hold the iothread lock whenever we > > > > call into various QEMU UI midlayer functions. > > > > > > > > > > I also think it's better to clarify that the reason of the commit is not > > > Mojave enforcing usage of event loop in main thread but an improvement > > > of event processing in Cocoa UI, because Cocoa UI works on Mojave. > > > > Hmm? The point of this patchset is exactly that Mojave enforces > > that things go on the main thread, where previous OSX versions > > did not, and so in some situations QEMU will crash on Mojave > > where it did not on older versions. So I'm not sure what you're > > suggesting should be clarified here. > > > > I'm not exactly sure there's an issue with QEMU on Mojave. But I lean > towards the opinion because I haven't seen it :)
It only happens for some guest workloads. The "usual" case is that the cocoa_refresh callback is called from the QEMU main loop, which happens to be on the OSX main thread, which means OSX is still happy. But in some cases cocoa_refresh can be called from a guest vCPU thread -- I think we've seen this when a guest initiates a screen resolution change: the call from the guest vCPU thread goes into the model of the graphics device, which makes a call into the UI midlayer to say "resolution changed", which immediately triggers a refresh callback to the UI frontend layer from that thread. In Mojave this causes OSX to terminate QEMU. I think in older OSX versions it would probably be a race condition, so it's technically a bug but not one that usually has any visible bad effects; it's only surfaced as a problem now that Mojave actively checks for this condition and kills the process. thanks -- PMM
