From: Jason Gunthorpe <jgg@ziepe.ca>
To: Jerome Glisse <jglisse@redhat.com>
Cc: Haggai Eran <haggaie@mellanox.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
Leon Romanovsky <leonro@mellanox.com>,
Doug Ledford <dledford@redhat.com>,
Artemy Kovalyov <artemyko@mellanox.com>,
Moni Shoua <monis@mellanox.com>,
Mike Marciniszyn <mike.marciniszyn@intel.com>,
Kaike Wan <kaike.wan@intel.com>,
Dennis Dalessandro <dennis.dalessandro@intel.com>,
Aviad Yehezkel <aviadye@mellanox.com>
Subject: Re: [PATCH 1/1] RDMA/odp: convert to use HMM for ODP
Date: Thu, 21 Feb 2019 15:59:37 -0700 [thread overview]
Message-ID: <20190221225937.GS17500@ziepe.ca> (raw)
In-Reply-To: <20190220222924.GE29398@redhat.com>
On Wed, Feb 20, 2019 at 05:29:24PM -0500, Jerome Glisse wrote:
> > >
> > > Yes it is safe, the hmm struct has its own refcount and mirror holds a
> > > reference on it, the mm struct itself has a reference on the mm
> > > struct.
> >
> > The issue here is that that hmm_mirror_unregister() must be a strong
> > fence that guarentees no callback is running or will run after
> > return. mmu_notifier_unregister did not provide that.
> >
> > I think I saw locking in hmm that was doing this..
>
> So pattern is:
> hmm_mirror_register(mirror);
>
> // Safe for driver to call within HMM with mirror no matter what
>
> hmm_mirror_unregister(mirror)
>
> // Driver must no stop calling within HMM, it would be a use after
> // free scenario
This statement is the opposite direction
I want to know that HMM doesn't allow any driver callbacks to be
running after unregister - because I am going to kfree mirror and
other memory touched by the driver callbacks.
Jason
next prev parent reply other threads:[~2019-02-21 22:59 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-29 16:58 [RFC PATCH 0/1] Use HMM for ODP jglisse
2019-01-29 16:58 ` [PATCH 1/1] RDMA/odp: convert to use " jglisse
2019-02-06 8:44 ` Haggai Eran
2019-02-12 16:11 ` Jerome Glisse
2019-02-13 6:28 ` Haggai Eran
2019-02-20 22:20 ` Jason Gunthorpe
2019-02-20 22:29 ` Jerome Glisse
2019-02-21 22:59 ` Jason Gunthorpe [this message]
2019-02-22 2:01 ` Jerome Glisse
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