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. > > 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
