On Fri, May 04, 2018 at 04:51:15PM +0800, 858585 jemmy wrote: > On Fri, May 4, 2018 at 11:14 AM, 858585 jemmy <jemmy858...@gmail.com> wrote: > > On Thu, May 3, 2018 at 11:33 PM, Jason Gunthorpe <j...@ziepe.ca> wrote: > >> On Thu, May 03, 2018 at 10:04:34PM +0800, Lidong Chen wrote: > >>> The userspace may invoke ibv_reg_mr and ibv_dereg_mr by different threads. > >>> If when ibv_dereg_mr invoke and the thread which invoked ibv_reg_mr has > >>> exited, get_pid_task will return NULL, ib_umem_release does not decrease > >>> mm->pinned_vm. This patch fixes it by use tgid. > >>> > >>> Signed-off-by: Lidong Chen <lidongc...@tencent.com> > >>> drivers/infiniband/core/umem.c | 12 ++++++------ > >>> include/rdma/ib_umem.h | 2 +- > >>> 2 files changed, 7 insertions(+), 7 deletions(-) > >> > >> Why are we even using a struct pid for this? Does anyone know? > > > > commit 87773dd56d5405ac28119fcfadacefd35877c18f add pid in ib_umem > > structure. > > > > and the comment has such information: > > Later a different process with a different mm_struct than the one that > > allocated the ib_umem struct > > ends up releasing it which results in decrementing the new processes > > mm->pinned_vm count past > > zero and wrapping. > > I think a different process should not have the permission to release ib_umem. > so maybe the reason is not a different process? > can ib_umem_release be invoked in interrupt context?
We plan to restore fork support and add some way to share MRs between processes, so we must consider having a different process release the umem than acquired it. Jason
