On Thu, Jun 02, 2022 at 10:49:15AM -0600, Logan Gunthorpe wrote: > > > On 2022-06-02 10:30, Jason Gunthorpe wrote: > > On Thu, Jun 02, 2022 at 10:16:10AM -0600, Logan Gunthorpe wrote: > > > >>> Just stuff the pages into the mmap, and your driver unprobe will > >>> automatically block until all the mmaps are closed - no different than > >>> having an open file descriptor or something. > >> > >> Oh is that what we want? > > > > Yes, it is the typical case - eg if you have a sysfs file open unbind > > hangs indefinitely. Many drivers can't unbind while they have open file > > descriptors/etc. > > > > A couple drivers go out of their way to allow unbinding while a live > > userspace exists but this can get complicated. Usually there should be > > a good reason. > > > > The module will already be refcounted anyhow because the mmap points > > to a char file which holds a module reference - meaning a simple rmmod > > of the driver shouldn't work already.. > > Also, I just tried it... If I open a sysfs file for an nvme device (ie. > /sys/class/nvme/nvme4/cntlid) and unbind the device, it does not block. > A subsequent read on that file descriptor returns ENODEV. Which is what > I would have expected. Oh interesting, this has been changed since years ago when I last looked, the kernfs_get_active() is now more narrowed than it once was. So manybe sysfs isn't the same concern it used to be! Thanks, Jason
