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    SubjectRe: [RFC PATCH 1/2] arm64: mm: Use READ_ONCE/WRITE_ONCE when accessing page tables
    On Wed, Sep 27, 2017 at 04:49:28PM +0100, Will Deacon wrote:
    > In many cases, page tables can be accessed concurrently by either another
    > CPU (due to things like fast gup) or by the hardware page table walker
    > itself, which may set access/dirty bits. In such cases, it is important
    > to use READ_ONCE/WRITE_ONCE when accessing page table entries so that
    > entries cannot be torn, merged or subject to apparent loss of coherence.

    In fact, we should use lockless_dereference() for many of them. Yes
    Alpha is the only one that cares about the difference between that and
    READ_ONCE() and they do have the extra barrier, but if we're going to do
    this, we might as well do it 'right' :-)

    Also, a very long standing item on my TODO list is to see how much of it
    we can unify across the various architectures, because there's a giant
    amount of boiler plate involved with all this.

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