On Mon, 2021-09-20 at 00:39 +0200, Halil Pasic wrote: > On Fri, 17 Sep 2021 10:40:20 +0200 > Cornelia Huck <cohuck@xxxxxxxxxx> wrote: > ...snip... > > > > > > Thanks, if I find time for it, I will try to understand this > > > better and > > > come back with my findings. > > > > > > > > * Can virtio_ccw_remove() get called while !cdev->online and > > > > > virtio_ccw_online() is running on a different cpu? If yes, > > > > > what would > > > > > happen then? > > > > > > > > All of the remove/online/... etc. callbacks are invoked via the > > > > ccw bus > > > > code. We have to trust that it gets it correct :) (Or have the > > > > common > > > > I/O layer maintainers double-check it.) > > > > > > > > > > Vineeth, what is your take on this? Are the struct ccw_driver > > > virtio_ccw_remove and the virtio_ccw_online callbacks mutually > > > exclusive. Please notice that we may initiate the onlining by > > > calling ccw_device_set_online() from a workqueue. > > > > > > @Conny: I'm not sure what is your definition of 'it gets it > > > correct'... > > > I doubt CIO can make things 100% foolproof in this area. > > > > Not 100% foolproof, but "don't online a device that is in the > > progress > > of going away" seems pretty basic to me. > > > > I hope Vineeth will chime in on this. Considering the online/offline processing, The ccw_device_set_offline function or the online/offline is handled inside device_lock. Also, the online_store function takes care of avoiding multiple online/offline processing. Now, when we consider the unconditional remove of the device, I am not familiar with the virtio_ccw driver. My assumptions are based on how CIO/dasd drivers works. If i understand correctly, the dasd driver sets different flags to make sure that a device_open is getting prevented while the the device is in progress of offline-ing. > > > > > > > > > > > > > > The main addresse of these questions is Conny ;). > > > ...snip...
