From: Andrew Morton <akpm@linux-foundation.org>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
stable@vger.kernel.org, Jason Gunthorpe <jgg@nvidia.com>,
John Hubbard <jhubbard@nvidia.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Hugh Dickins <hughd@google.com>, Peter Xu <peterx@redhat.com>,
Alistair Popple <apopple@nvidia.com>,
Nadav Amit <namit@vmware.com>, Yang Shi <shy828301@gmail.com>,
Vlastimil Babka <vbabka@suse.cz>,
Michal Hocko <mhocko@kernel.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Andrea Parri <parri.andrea@gmail.com>,
Will Deacon <will@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
Christoph von Recklinghausen <crecklin@redhat.com>,
Don Dutile <ddutile@redhat.com>
Subject: Re: [PATCH v1] mm: fix PageAnonExclusive clearing racing with concurrent RCU GUP-fast
Date: Thu, 1 Sep 2022 15:35:12 -0700 [thread overview]
Message-ID: <20220901153512.a59e9e584fb00a350788f56e@linux-foundation.org> (raw)
In-Reply-To: <20220901083559.67446-1-david@redhat.com>
On Thu, 1 Sep 2022 10:35:59 +0200 David Hildenbrand <david@redhat.com> wrote:
> The possible issues due to reordering are of theoretical nature so far
> and attempts to reproduce the race failed.
>
> Especially the "no PTE change" case isn't the common case, because we'd
> need an exclusive anonymous page that's mapped R/O and the PTE is clean
> in KSM code -- and using KSM with page pinning isn't extremely common.
> Further, the clear+TLB flush we used for now implies a memory barrier.
> So the problematic missing part should be the missing memory barrier
> after pinning but before checking if the PTE changed.
Obscure bug, large and tricky patch. Is a -stable backport really
justifiable?
next prev parent reply other threads:[~2022-09-01 22:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-01 8:35 [PATCH v1] mm: fix PageAnonExclusive clearing racing with concurrent RCU GUP-fast David Hildenbrand
2022-09-01 22:35 ` Andrew Morton [this message]
2022-09-02 6:49 ` David Hildenbrand
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220901153512.a59e9e584fb00a350788f56e@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=aarcange@redhat.com \
--cc=apopple@nvidia.com \
--cc=crecklin@redhat.com \
--cc=david@redhat.com \
--cc=ddutile@redhat.com \
--cc=hughd@google.com \
--cc=jgg@nvidia.com \
--cc=jhubbard@nvidia.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=mike.kravetz@oracle.com \
--cc=namit@vmware.com \
--cc=parri.andrea@gmail.com \
--cc=paulmck@kernel.org \
--cc=peterx@redhat.com \
--cc=peterz@infradead.org \
--cc=shy828301@gmail.com \
--cc=stable@vger.kernel.org \
--cc=vbabka@suse.cz \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).