From: Jerome Glisse <jglisse@redhat.com>
To: Jason Gunthorpe <jgg@mellanox.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>,
John Hubbard <jhubbard@nvidia.com>,
"Felix.Kuehling@amd.com" <Felix.Kuehling@amd.com>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Andrea Arcangeli <aarcange@redhat.com>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"amd-gfx@lists.freedesktop.org" <amd-gfx@lists.freedesktop.org>,
Ben Skeggs <bskeggs@redhat.com>, Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH hmm 02/15] mm/mmu_notifier: add an interval tree notifier
Date: Mon, 21 Oct 2019 15:47:48 -0400 [thread overview]
Message-ID: <20191021194748.GA5644@redhat.com> (raw)
In-Reply-To: <20191021192448.GK6285@mellanox.com>
On Mon, Oct 21, 2019 at 07:24:53PM +0000, Jason Gunthorpe wrote:
> On Mon, Oct 21, 2019 at 03:11:57PM -0400, Jerome Glisse wrote:
> > > Since that reader is not locked we need release semantics here to
> > > ensure the unlocked reader sees a fully initinalized mmu_notifier_mm
> > > structure when it observes the pointer.
> >
> > I thought the mm_take_all_locks() would have had a barrier and thus
> > that you could not see mmu_notifier struct partialy initialized.
>
> Not sure, usually a lock acquire doesn't have a store barrier?
Yeah likely.
>
> Even if it did, we would still need some pairing read barrier..
>
> > having the acquire/release as safety net does not hurt. Maybe add a
> > comment about the struct initialization needing to be visible before
> > pointer is set.
>
> Is this clear?
>
> * release semantics on the initialization of the
> * mmu_notifier_mm's contents are provided for unlocked readers.
> * acquire can only be used while holding the
> * mmgrab or mmget, and is safe because once created the
> * mmu_notififer_mm is not freed until the mm is destroyed.
> * Users holding the mmap_sem or one of the
> * mm_take_all_locks() do not need to use acquire semantics.
>
> It also helps explain why there is no locking around the other
> readers, which has puzzled me in the past at least.
Perfect.
Jérôme
next prev parent reply other threads:[~2019-10-21 19:47 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-15 18:12 [PATCH hmm 00/15] Consolidate the mmu notifier interval_tree and locking Jason Gunthorpe
2019-10-15 18:12 ` [PATCH hmm 01/15] mm/mmu_notifier: define the header pre-processor parts even if disabled Jason Gunthorpe
2019-10-21 18:32 ` Jerome Glisse
2019-10-15 18:12 ` [PATCH hmm 02/15] mm/mmu_notifier: add an interval tree notifier Jason Gunthorpe
2019-10-21 18:30 ` Jerome Glisse
2019-10-21 18:54 ` Jason Gunthorpe
2019-10-21 19:11 ` Jerome Glisse
2019-10-21 19:24 ` Jason Gunthorpe
2019-10-21 19:47 ` Jerome Glisse [this message]
2019-10-27 23:15 ` Jason Gunthorpe
2019-10-15 18:12 ` [PATCH hmm 03/15] mm/hmm: allow hmm_range to be used with a mmu_range_notifier or hmm_mirror Jason Gunthorpe
2019-10-21 18:33 ` Jerome Glisse
2019-10-15 18:12 ` [PATCH hmm 04/15] mm/hmm: define the pre-processor related parts of hmm.h even if disabled Jason Gunthorpe
2019-10-21 18:31 ` Jerome Glisse
2019-10-15 18:12 ` [PATCH hmm 05/15] RDMA/odp: Use mmu_range_notifier_insert() Jason Gunthorpe
2019-11-04 20:25 ` Jason Gunthorpe
2019-10-15 18:12 ` [PATCH hmm 06/15] RDMA/hfi1: Use mmu_range_notifier_inset for user_exp_rcv Jason Gunthorpe
2019-10-29 12:15 ` Dennis Dalessandro
2019-10-15 18:12 ` [PATCH hmm 07/15] drm/radeon: use mmu_range_notifier_insert Jason Gunthorpe
2019-10-15 18:12 ` [PATCH hmm 08/15] xen/gntdev: Use select for DMA_SHARED_BUFFER Jason Gunthorpe
2019-10-16 5:11 ` Jürgen Groß
2019-10-16 6:35 ` Oleksandr Andrushchenko
2019-10-21 19:12 ` Jason Gunthorpe
2019-10-28 6:25 ` [Xen-devel] " Oleksandr Andrushchenko
2019-10-15 18:12 ` [PATCH hmm 09/15] xen/gntdev: use mmu_range_notifier_insert Jason Gunthorpe
2019-10-15 18:12 ` [PATCH hmm 10/15] nouveau: use mmu_notifier directly for invalidate_range_start Jason Gunthorpe
2019-10-15 18:12 ` [PATCH hmm 11/15] nouveau: use mmu_range_notifier instead of hmm_mirror Jason Gunthorpe
2019-10-15 18:12 ` [PATCH hmm 12/15] drm/amdgpu: Call find_vma under mmap_sem Jason Gunthorpe
2019-10-15 18:12 ` [PATCH hmm 13/15] drm/amdgpu: Use mmu_range_insert instead of hmm_mirror Jason Gunthorpe
2019-10-15 18:12 ` [PATCH hmm 14/15] drm/amdgpu: Use mmu_range_notifier " Jason Gunthorpe
2019-10-15 18:12 ` [PATCH hmm 15/15] mm/hmm: remove hmm_mirror and related Jason Gunthorpe
2019-10-21 18:38 ` Jerome Glisse
2019-10-21 18:57 ` Jason Gunthorpe
2019-10-21 19:19 ` Jerome Glisse
2019-10-16 8:58 ` [PATCH hmm 00/15] Consolidate the mmu notifier interval_tree and locking Christian König
2019-10-16 16:04 ` Jason Gunthorpe
2019-10-17 8:54 ` Christian König
2019-10-17 16:26 ` Yang, Philip
2019-10-17 16:47 ` Koenig, Christian
2019-10-18 20:36 ` Jason Gunthorpe
2019-10-20 14:21 ` Koenig, Christian
2019-10-21 13:57 ` Jason Gunthorpe
2019-10-21 14:28 ` Koenig, Christian
2019-10-21 15:12 ` Jason Gunthorpe
2019-10-22 7:57 ` Daniel Vetter
2019-10-22 15:01 ` Jason Gunthorpe
2019-10-23 9:08 ` Daniel Vetter
2019-10-23 9:32 ` Christian König
2019-10-23 16:52 ` Jerome Glisse
2019-10-23 17:24 ` Jason Gunthorpe
2019-10-24 2:16 ` Christoph Hellwig
2019-10-21 15:55 ` Dennis Dalessandro
2019-10-21 16:58 ` Jason Gunthorpe
2019-10-22 11:56 ` Dennis Dalessandro
2019-10-22 14:37 ` Jason Gunthorpe
2019-10-21 18:40 ` Jerome Glisse
2019-10-21 19:06 ` Jason Gunthorpe
2019-10-23 20:26 ` Jerome Glisse
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191021194748.GA5644@redhat.com \
--to=jglisse@redhat.com \
--cc=Felix.Kuehling@amd.com \
--cc=aarcange@redhat.com \
--cc=amd-gfx@lists.freedesktop.org \
--cc=bskeggs@redhat.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=jgg@mellanox.com \
--cc=jhubbard@nvidia.com \
--cc=linux-mm@kvack.org \
--cc=linux-rdma@vger.kernel.org \
--cc=mhocko@kernel.org \
--cc=rcampbell@nvidia.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).