On Fri, May 04, 2018 at 04:32:38PM +0800, 858585 jemmy wrote: > On Fri, May 4, 2018 at 6:01 AM, Jason Gunthorpe <jgg@xxxxxxxx> wrote: > > On Thu, May 03, 2018 at 09:43:01PM +0300, Leon Romanovsky wrote: > >> On Thu, May 03, 2018 at 12:26:56PM -0600, Jason Gunthorpe wrote: > >> > On Thu, May 03, 2018 at 09:12:35PM +0300, Leon Romanovsky wrote: > >> > > On Thu, May 03, 2018 at 09:33:10AM -0600, Jason Gunthorpe 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? > >> > > > > >> > > > >> > > Can it be related to "fork" support? > >> > > >> > Not sure.. > >> > > >> > Ideally we want to hold the struct mm, but we can't hold it long > >> > term, so pid is a surrogate for that. > >> > > >> > > > I'm surprised that struct task isn't held in the struct ib_umem.. > >> > > > > >> > > > >> > > I think that this code can be removed and all accesses to mm_struct can > >> > > be done with "current->mm". > >> > > >> > That sounds wrong for fork support, as the mm used in destroy MUST > >> > exactly match the mm used in create.. > >> > > >> > How does this accounting work in fork anyhow? > >> > >> We are not supporting fork, so this is why I proposed to remove it. > > > > Er, the new kabi certainly can call reg and dereg across a fork > > what is the expect behavior after fork? > I write a test code, the dereg just return EACCES in the child > process. and have no effect. Did you do reg/dereg over write() interface? If yes, this is expected behaviour of "not-supported fork()". A couple of months/years ago, your test program would work, but we closed this option due to security constraints. Thanks > > > > > Jason
Attachment:
signature.asc
Description: PGP signature
