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Message-ID: <CAOUHufbwyCRHx07e5VrDuG60X5wRUJ795qcBOz3u+ZEmx0Bgog@mail.gmail.com>
Date: Wed, 24 May 2023 16:54:59 -0600
From: Yu Zhao <yuzhao@...gle.com>
To: Hugh Dickins <hughd@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Mike Kravetz <mike.kravetz@...cle.com>,
Mike Rapoport <rppt@...nel.org>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Matthew Wilcox <willy@...radead.org>,
David Hildenbrand <david@...hat.com>,
Suren Baghdasaryan <surenb@...gle.com>,
Qi Zheng <zhengqi.arch@...edance.com>,
Yang Shi <shy828301@...il.com>,
Mel Gorman <mgorman@...hsingularity.net>,
Peter Xu <peterx@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Will Deacon <will@...nel.org>,
Alistair Popple <apopple@...dia.com>,
Ralph Campbell <rcampbell@...dia.com>,
Ira Weiny <ira.weiny@...el.com>,
Steven Price <steven.price@....com>,
SeongJae Park <sj@...nel.org>,
Naoya Horiguchi <naoya.horiguchi@....com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Zack Rusin <zackr@...are.com>, Jason Gunthorpe <jgg@...pe.ca>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Anshuman Khandual <anshuman.khandual@....com>,
Pasha Tatashin <pasha.tatashin@...een.com>,
Miaohe Lin <linmiaohe@...wei.com>,
Minchan Kim <minchan@...nel.org>,
Christoph Hellwig <hch@...radead.org>,
Song Liu <song@...nel.org>,
Thomas Hellstrom <thomas.hellstrom@...ux.intel.com>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 01/31] mm: use pmdp_get_lockless() without surplus barrier()
On Sun, May 21, 2023 at 10:49 PM Hugh Dickins <hughd@...gle.com> wrote:
>
> Use pmdp_get_lockless() in preference to READ_ONCE(*pmdp), to get a more
> reliable result with PAE (or READ_ONCE as before without PAE); and remove
> the unnecessary extra barrier()s which got left behind in its callers.
>
> HOWEVER: Note the small print in linux/pgtable.h, where it was designed
> specifically for fast GUP, and depends on interrupts being disabled for
> its full guarantee: most callers which have been added (here and before)
> do NOT have interrupts disabled, so there is still some need for caution.
>
> Signed-off-by: Hugh Dickins <hughd@...gle.com>
Acked-by: Yu Zhao <yuzhao@...gle.com>
The previous ask here:
https://lore.kernel.org/r/CAOUHufZo=fB2HcaCrj2aidLJ2zEhOpi7ou5M_7qOQiuQq8+wTQ@mail.gmail.com/
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