> Even more interestingly the function ipath_user_sdma_queue_pkts() (and > also > ipath_user_sdma_coalesce() called somewhat later) call copy_from_user() > which can hit a page fault and we deadlock on trying to get mmap_sem > when handling that fault. So just make ipath_user_sdma_pin_pages() use > get_user_pages_fast() and leave mmap_sem locking for mm. > > This deadlock has actually been observed in the wild when the node is under > memory pressure.
This patch has been re-submited in http://marc.info/?l=linux-rdma&m=138089335106353&w=2. Mike
