On Sat, May 5, 2018 at 2:23 AM, Jason Gunthorpe <jgg@xxxxxxxx> wrote: > On Fri, May 04, 2018 at 04:51:15PM +0800, 858585 jemmy wrote: >> On Fri, May 4, 2018 at 11:14 AM, 858585 jemmy <jemmy858585@xxxxxxxxx> wrote: >> > On Thu, May 3, 2018 at 11:33 PM, Jason Gunthorpe <jgg@xxxxxxxx> 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 <lidongchen@xxxxxxxxxxx> >> >>> 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. If restore fork support, what is the expected behavior? If parent process pinned_vm is x, what is the child process pinned_vm value after fork? It reset to zero now. If the parent process call ibv_dereg_mr after fork, should the child process decrease pinned_vm? If the child process call ibv_dereg_mr after fork, should the parent process decrease pinned_vm? > > Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
