On 2023-11-08 17:20, 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(). > My understanding is that the lock is there not for reference counting but to prevent concurrent reprogramming of the region by in-kernel API consumers. >>>> Could you help elaborate more about the race? >>>> >>> >>> I accidentally misused the word race. My concern was that memory might >>> be released after the last put_device(), causing mutex_unlock() to be >>> called on a mutex that does not exist anymore. It should not happen >>> for the moment since the region does not use devres, but I think it >>> still makes the code more brittle. >> >> It makes sense. >> Thanks, Marco
