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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon, 24 Oct 2022 13:36:23 -0700
Message-ID: <CAHk-=whE3+pLUQrzK=f0_GKdYZrv=72ox2nQrPhc+jZCMLqVSw@mail.gmail.com>
Subject: Re: [PATCH 01/13] mm: Update ptep_get_lockless()s comment
To:     Jann Horn <jannh@google.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        John Hubbard <jhubbard@nvidia.com>, x86@kernel.org,
        willy@infradead.org, akpm@linux-foundation.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        aarcange@redhat.com, kirill.shutemov@linux.intel.com,
        jroedel@suse.de, ubizjak@gmail.com
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On Mon, Oct 24, 2022 at 1:24 PM Jann Horn <jannh@google.com> wrote:
>
> That's why GUP-fast re-checks the PTE after it has grabbed a reference
> to the page.

Bah. I should have known that. We got that through the PPC version
that never had the whole IPI serialization thing (just the RCU
freeing).

I haven't looked at that code in much too long.

Actually, by "much too long" I really mean "thankfully I haven't needed to" ;)

                 Linus