On Wed, Feb 23, 2022 at 09:46:27AM -0400, Jason Gunthorpe wrote: > On Wed, Feb 23, 2022 at 01:04:00PM +0000, Robin Murphy wrote: > > > 1 - tmp->driver is non-NULL because tmp is already bound. > > 1.a - If tmp->driver->driver_managed_dma == 0, the group must currently be > > DMA-API-owned as a whole. Regardless of what driver dev has unbound from, > > its removal does not release someone else's DMA API (co-)ownership. > > This is an uncommon locking pattern, but it does work. It relies on > the mutex being an effective synchronization barrier for an unlocked > store: > > WRITE_ONCE(dev->driver, NULL) Only the driver core should be messing with the dev->driver pointer as when it does so, it already has the proper locks held. Do I need to move that to a "private" location so that nothing outside of the driver core can mess with it? thanks, greg k-h
