lkml.org 
[lkml]   [2018]   [May]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] IB/umem: use tgid instead of pid in ib_umem structure
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@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?
> > >
> >
> > 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
[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2018-05-03 20:43    [W:0.080 / U:5.852 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site