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Date: Tue, 20 Feb 2018 10:34:49 -0800
From: Mark Hairgrove <mhairgrove@nvidia.com>
To: Balbir Singh <bsingharora@gmail.com>
CC: Alistair Popple <alistair@popple.id.au>, <mpe@ellerman.id.au>,
 <linuxppc-dev@lists.ozlabs.org>, Javier Cabezas <jcabezas@nvidia.com>
Subject: Re: [PATCH] powerpc/npu-dma.c: Fix deadlock in mmio_invalidate
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On Mon, 19 Feb 2018, Balbir Singh wrote:

> Good point, although I think the acquire_* function itself may be called
> from a higher layer with the mmap_sem always held. I wonder if we need
> barriers around get and put mmio_atsd_reg.

I agree with the need for memory barriers. FWIW, page tables can be
invalidated without mmap_sem being held, for example by
unmap_mapping_range.