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. Logan
