On Tue, Aug 13, 2019 at 08:57:07AM -0300, Jason Gunthorpe wrote: > On Tue, Aug 13, 2019 at 04:31:07PM +0800, Jason Wang wrote: > > > What kind of issues do you see? Spinlock is to synchronize GUP with MMU > > notifier in this series. > > A GUP that can't sleep can't pagefault which makes it a really weird > pattern
get_user_pages/get_user_pages_fast must not be called under a spinlock. We have the somewhat misnamed __get_user_page_fast that just does a lookup for existing pages and never faults for a few places that need to do that lookup from contexts where we can't sleep.
