From: Peter Zijlstra <peterz@infradead.org>
To: Will Deacon <will.deacon@arm.com>
Cc: paulmck@linux.vnet.ibm.com, kirill.shutemov@linux.intel.com,
linux-kernel@vger.kernel.org, ynorov@caviumnetworks.com,
rruigrok@codeaurora.org, linux-arch@vger.kernel.org,
akpm@linux-foundation.org, catalin.marinas@arm.com
Subject: Re: [RFC PATCH 1/2] arm64: mm: Use READ_ONCE/WRITE_ONCE when accessing page tables
Date: Thu, 28 Sep 2017 10:38:01 +0200 [thread overview]
Message-ID: <20170928083801.m6rb4frbbgzgam2o@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1506527369-19535-2-git-send-email-will.deacon@arm.com>
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.
next prev parent reply other threads:[~2017-09-28 8:38 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-27 15:49 [RFC PATCH 0/2] Missing READ_ONCE in core and arch-specific pgtable code leading to crashes Will Deacon
2017-09-27 15:49 ` [RFC PATCH 1/2] arm64: mm: Use READ_ONCE/WRITE_ONCE when accessing page tables Will Deacon
2017-09-28 8:38 ` Peter Zijlstra [this message]
2017-09-28 8:45 ` Will Deacon
2017-09-28 15:43 ` Paul E. McKenney
2017-09-28 15:49 ` Will Deacon
2017-09-28 16:07 ` Paul E. McKenney
2017-09-28 18:59 ` Michael Cree
2017-09-29 0:58 ` Paul E. McKenney
2017-09-29 9:08 ` Will Deacon
2017-09-29 16:29 ` Paul E. McKenney
2017-09-29 16:33 ` Will Deacon
2017-10-03 19:11 ` Paul E. McKenney
2017-10-05 16:31 ` Will Deacon
2017-10-05 19:22 ` Paul E. McKenney
2017-10-05 19:31 ` Andrea Parri
2017-10-05 20:09 ` Paul E. McKenney
2017-09-28 19:18 ` Timur Tabi
2017-09-27 15:49 ` [RFC PATCH 2/2] mm: page_vma_mapped: Ensure pmd is loaded with READ_ONCE outside of lock Will Deacon
2017-09-27 22:01 ` [RFC PATCH 0/2] Missing READ_ONCE in core and arch-specific pgtable code leading to crashes Yury Norov
2017-09-28 17:30 ` Richard Ruigrok
2017-09-28 19:38 ` Jon Masters
2017-09-29 8:56 ` Will Deacon
2017-10-03 6:36 ` Jon Masters
2017-10-05 16:54 ` Will Deacon
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