From: Jan Stancek <jstancek@redhat.com>
To: Andrea Arcangeli <aarcange@redhat.com>, peterz@infradead.org
Cc: linux-mm@kvack.org, akpm@linux-foundation.org,
willy@infradead.org, riel@surriel.com, mhocko@suse.com,
ying huang <ying.huang@intel.com>,
jrdr linux <jrdr.linux@gmail.com>,
jglisse@redhat.com, aneesh kumar <aneesh.kumar@linux.ibm.com>,
david@redhat.com, raquini@redhat.com, rientjes@google.com,
kirill@shutemov.name, mgorman@techsingularity.net,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm/memory.c: do_fault: avoid usage of stale vm_area_struct
Date: Sun, 3 Mar 2019 02:27:02 -0500 (EST) [thread overview]
Message-ID: <701776300.4537344.1551598022408.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <20190302185144.GD31083@redhat.com>
----- Original Message -----
> Hello Jan,
>
> On Sat, Mar 02, 2019 at 07:19:39PM +0100, Jan Stancek wrote:
> > + struct mm_struct *vm_mm = READ_ONCE(vma->vm_mm);
>
> The vma->vm_mm cannot change under gcc there, so no need of
> READ_ONCE. The release of mmap_sem has release semantics so the
> vma->vm_mm access cannot be reordered after up_read(mmap_sem) either.
>
> Other than the above detail:
>
> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Thank you for review, I dropped READ_ONCE and sent v3 with your
Reviewed-by included. I also successfully re-ran tests over-night.
> Would this not need a corresponding WRITE_ONCE() in vma_init() ?
There's at least 2 context switches between, so I think it wouldn't matter.
My concern was gcc optimizing out vm_mm, and vma->vm_mm access happening only
after do_read_fault().
next prev parent reply other threads:[~2019-03-03 7:27 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-02 15:11 [PATCH] mm/memory.c: do_fault: avoid usage of stale vm_area_struct Jan Stancek
2019-03-02 17:10 ` Matthew Wilcox
2019-03-02 18:00 ` Jan Stancek
2019-03-02 18:19 ` [PATCH v2] " Jan Stancek
2019-03-02 18:45 ` Peter Zijlstra
2019-03-02 18:51 ` Andrea Arcangeli
2019-03-03 7:27 ` Jan Stancek [this message]
2019-03-03 7:28 ` [PATCH v3] " Jan Stancek
2019-03-03 10:36 ` Matthew Wilcox
2019-03-04 0:13 ` Rafael Aquini
2019-03-04 8:10 ` Minchan Kim
2019-03-04 8:19 ` Kirill A. Shutemov
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