On Tue, May 20, 2025 at 03:20:00PM -0700, Sean Christopherson wrote: > On Tue, May 20, 2025, Peter Zijlstra wrote: > > On Mon, May 19, 2025 at 11:55:10AM -0700, Sean Christopherson wrote: > > > Drop the setting of WQ_FLAG_EXCLUSIVE from add_wait_queue_priority() to > > > differentiate it from add_wait_queue_priority_exclusive(). The one and > > > only user add_wait_queue_priority(), Xen privcmd's irqfd_wakeup(), > > > unconditionally returns '0', i.e. doesn't actually operate in exclusive > > > mode. > > > > I find: > > > > drivers/hv/mshv_eventfd.c: add_wait_queue_priority(wqh, &irqfd->irqfd_wait); > > drivers/xen/privcmd.c: add_wait_queue_priority(wqh, &kirqfd->wait); > > > > I mean, it might still be true and all, but hyperv seems to also use > > this now. > > Oh FFS, another "heavily inspired by KVM". I should have bribed someone to take > this series when I had the chance. *sigh* > > Unfortunately, the Hyper-V code does actually operate in exclusive mode. Unless > you have a better idea, I'll tweak the series to: > > 1. Drop WQ_FLAG_EXCLUSIVE from add_wait_queue_priority() and have the callers > explicitly set the flag, > 2. Add a patch to drop WQ_FLAG_EXCLUSIVE from Xen privcmd entirely. > 3. Introduce add_wait_queue_priority_exclusive() and switch KVM to use it. > > That has an added bonus of introducing the Xen change in a dedicated patch, i.e. > is probably a sequence anyways. > > Alternatively, I could rewrite the Hyper-V code a la the KVM changes, but I'm not > feeling very charitable at the moment (the complete lack of documentation for > their ioctl doesn't help). Works for me. Michael is typically very responsive wrt hyperv (but you probably know this).
