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. Thanks > > Jason
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