From: Jason Gunthorpe <jgg@ziepe.ca>
To: Leon Romanovsky <leon@kernel.org>
Cc: Lidong Chen <jemmy858585@gmail.com>,
dledford@redhat.com, akpm@linux-foundation.org,
qing.huang@oracle.com, artemyko@mellanox.com,
dan.j.williams@intel.com, linux-rdma@vger.kernel.org,
linux-kernel@vger.kernel.org, adido@mellanox.com,
galsha@mellanox.com, aviadye@mellanox.com,
Lidong Chen <lidongchen@tencent.com>
Subject: Re: [PATCH] IB/umem: use tgid instead of pid in ib_umem structure
Date: Thu, 3 May 2018 16:01:48 -0600 [thread overview]
Message-ID: <20180503220148.GC14956@ziepe.ca> (raw)
In-Reply-To: <20180503184301.GD4473@mtr-leonro.local>
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@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.
Er, the new kabi certainly can call reg and dereg across a fork
Jason
next prev parent reply other threads:[~2018-05-03 22:01 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-03 14:04 [PATCH] IB/umem: use tgid instead of pid in ib_umem structure Lidong Chen
2018-05-03 15:33 ` Jason Gunthorpe
2018-05-03 18:12 ` Leon Romanovsky
2018-05-03 18:26 ` Jason Gunthorpe
2018-05-03 18:43 ` Leon Romanovsky
2018-05-03 22:01 ` Jason Gunthorpe [this message]
2018-05-04 8:32 ` 858585 jemmy
2018-05-04 13:39 ` Leon Romanovsky
2018-05-04 15:14 ` lidongchen(陈立东)
2018-05-04 2:41 ` 858585 jemmy
2018-05-04 3:14 ` 858585 jemmy
2018-05-04 8:51 ` 858585 jemmy
2018-05-04 18:23 ` Jason Gunthorpe
2018-05-07 1:38 ` 858585 jemmy
2018-05-08 6:30 ` Jason Gunthorpe
2018-05-08 8:32 ` 858585 jemmy
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