From: Ralph Campbell <rcampbell@nvidia.com>
To: Jason Gunthorpe <jgg@ziepe.ca>, <linux-mm@kvack.org>
Cc: "Andrea Arcangeli" <aarcange@redhat.com>,
"Christoph Hellwig" <hch@lst.de>,
"John Hubbard" <jhubbard@nvidia.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Kuehling, Felix" <Felix.Kuehling@amd.com>,
"Alex Deucher" <alexander.deucher@amd.com>,
"Christian König" <christian.koenig@amd.com>,
"David (ChunMing) Zhou" <David1.Zhou@amd.com>,
"Dimitri Sivanich" <sivanich@sgi.com>,
dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org,
linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org,
iommu@lists.linux-foundation.org,
intel-gfx@lists.freedesktop.org,
"Gavin Shan" <shangw@linux.vnet.ibm.com>,
"Andrea Righi" <andrea@betterlinux.com>,
"Jason Gunthorpe" <jgg@mellanox.com>
Subject: Re: [PATCH v3 hmm 02/11] mm/mmu_notifiers: do not speculatively allocate a mmu_notifier_mm
Date: Wed, 14 Aug 2019 13:32:13 -0700 [thread overview]
Message-ID: <d2d8d6a8-7ac5-8f04-c11a-61140fccc5e1@nvidia.com> (raw)
In-Reply-To: <20190806231548.25242-3-jgg@ziepe.ca>
On 8/6/19 4:15 PM, Jason Gunthorpe wrote:
> From: Jason Gunthorpe <jgg@mellanox.com>
>
> A prior commit e0f3c3f78da2 ("mm/mmu_notifier: init notifier if necessary")
> made an attempt at doing this, but had to be reverted as calling
> the GFP_KERNEL allocator under the i_mmap_mutex causes deadlock, see
> commit 35cfa2b0b491 ("mm/mmu_notifier: allocate mmu_notifier in advance").
>
> However, we can avoid that problem by doing the allocation only under
> the mmap_sem, which is already happening.
>
> Since all writers to mm->mmu_notifier_mm hold the write side of the
> mmap_sem reading it under that sem is deterministic and we can use that to
> decide if the allocation path is required, without speculation.
>
> The actual update to mmu_notifier_mm must still be done under the
> mm_take_all_locks() to ensure read-side coherency.
>
> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Looks good to me.
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
next prev parent reply other threads:[~2019-08-14 20:32 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-06 23:15 [PATCH v3 hmm 00/11] Add mmu_notifier_get/put for managing mmu notifier registrations Jason Gunthorpe
2019-08-06 23:15 ` [PATCH v3 hmm 01/11] mm/mmu_notifiers: hoist do_mmu_notifier_register down_write to the caller Jason Gunthorpe
2019-08-08 10:24 ` Christoph Hellwig
2019-08-14 20:14 ` Ralph Campbell
2019-08-06 23:15 ` [PATCH v3 hmm 02/11] mm/mmu_notifiers: do not speculatively allocate a mmu_notifier_mm Jason Gunthorpe
2019-08-08 10:26 ` Christoph Hellwig
2019-08-14 20:32 ` Ralph Campbell [this message]
2019-08-06 23:15 ` [PATCH v3 hmm 03/11] mm/mmu_notifiers: add a get/put scheme for the registration Jason Gunthorpe
2019-08-14 21:20 ` Ralph Campbell
2019-08-15 0:13 ` Jason Gunthorpe
2019-08-06 23:15 ` [PATCH v3 hmm 04/11] misc/sgi-gru: use mmu_notifier_get/put for struct gru_mm_struct Jason Gunthorpe
2019-08-08 10:25 ` Christoph Hellwig
2019-08-14 15:58 ` Jason Gunthorpe
2019-08-14 17:18 ` Dimitri Sivanich
2019-08-06 23:15 ` [PATCH v3 hmm 05/11] hmm: use mmu_notifier_get/put for 'struct hmm' Jason Gunthorpe
2019-08-08 10:28 ` Christoph Hellwig
2019-08-14 21:51 ` Ralph Campbell
2019-08-06 23:15 ` [PATCH v3 hmm 06/11] RDMA/odp: use mmu_notifier_get/put for 'struct ib_ucontext_per_mm' Jason Gunthorpe
2019-08-06 23:15 ` [PATCH v3 hmm 07/11] RDMA/odp: remove ib_ucontext from ib_umem Jason Gunthorpe
2019-08-06 23:15 ` [PATCH v3 hmm 08/11] drm/radeon: use mmu_notifier_get/put for struct radeon_mn Jason Gunthorpe
2019-08-14 16:07 ` Jason Gunthorpe
2019-08-15 8:28 ` Christian König
2019-08-15 19:46 ` Jason Gunthorpe
2019-08-06 23:15 ` [PATCH v3 hmm 09/11] drm/amdkfd: fix a use after free race with mmu_notifer unregister Jason Gunthorpe
2019-08-06 23:15 ` [PATCH v3 hmm 10/11] drm/amdkfd: use mmu_notifier_put Jason Gunthorpe
2019-08-06 23:47 ` Kuehling, Felix
2019-08-07 11:42 ` Jason Gunthorpe
2019-08-06 23:15 ` [PATCH v3 hmm 11/11] mm/mmu_notifiers: remove unregister_no_release Jason Gunthorpe
2019-08-08 10:29 ` Christoph Hellwig
2019-08-14 21:53 ` Ralph Campbell
2019-08-14 23:56 ` [PATCH v3 hmm 00/11] Add mmu_notifier_get/put for managing mmu notifier registrations Ralph Campbell
2019-08-16 15:14 ` Jason Gunthorpe
2019-08-21 19:53 ` Jason Gunthorpe
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