On Thu, Nov 09, 2023 at 03:16:26PM +0800, Xu Yilun wrote: > On Thu, Nov 09, 2023 at 06:27:24AM +0100, Greg Kroah-Hartman wrote: > > On Thu, Nov 09, 2023 at 01:07:42PM +0800, Xu Yilun wrote: > > > On Wed, Nov 08, 2023 at 05:20:53PM +0100, Greg Kroah-Hartman wrote: > > > > On Wed, Nov 08, 2023 at 11:52:52PM +0800, Xu Yilun wrote: > > > > > > >> > > > > > > >> In fpga_region_get() / fpga_region_put(): call get_device() before > > > > > > >> acquiring the mutex and put_device() after having released the mutex > > > > > > >> to avoid races. > > > > > > > > Why do you need another reference count with a lock? You already have > > > > that with the calls to get/put_device(). > > > > > > The low-level driver module could still be possibly unloaded at the same > > > time, if so, when FPGA core run some callbacks provided by low-level driver > > > module, its referenced page of code is unmapped... > > > > Then something is designed wrong here, the unloading of the low-level > > driver should remove the access to the device itself. Perhaps fix that? > > Actually the low-level driver module on its own has no way to garantee its > own code page of callbacks not accessed. It *is* accessing its code page > when it tries (to release) any protection. It is not up to the low-level driver to do this, it's up to the code that calls into it (i.e. the fpga core code) to handle the proper reference counting. > Core code must help, and something like file_operations.owner is an > effective way. Yes, that should be all that you need. thanks, greg k-h
