From: Will Deacon <will@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jens Axboe <axboe@kernel.dk>,
Richard Earnshaw <Richard.Earnshaw@arm.com>,
Vincent Whitchurch <rabinv@axis.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Vincent Whitchurch <vincent.whitchurch@axis.com>,
Russell King - ARM Linux <linux@armlinux.org.uk>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2] buffer: Fix I/O error due to ARM read-after-read hazard
Date: Wed, 13 Nov 2019 10:23:58 +0000 [thread overview]
Message-ID: <20191113102357.GA25875@willie-the-truck> (raw)
In-Reply-To: <CAHk-=wg4vi27mnMVgZ-rzcEdDAjTXrY1Jyz3+=5STcY0bw4-jQ@mail.gmail.com>
On Tue, Nov 12, 2019 at 10:39:01AM -0800, Linus Torvalds wrote:
> On Tue, Nov 12, 2019 at 10:22 AM Catalin Marinas
> <catalin.marinas@arm.com> wrote:
> >
> > OK, so this includes changing test_bit() to perform a READ_ONCE.
>
> That's not going to happen.
Ok, I'll stick my neck out here, but if test_bit() is being used to read
a bitmap that is being concurrently modified (e.g. by set_bit() which boils
down to atomic_long_or()), then why isn't READ_ONCE() required? Right now,
test_bit takes a 'const volatile unsigned long *addr' argument, so I don't
see that you'll get a change in codegen except on alpha and, with this
erratum, arm32.
Will
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next prev parent reply other threads:[~2019-11-13 10:24 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-12 13:02 [PATCH v2] buffer: Fix I/O error due to ARM read-after-read hazard Vincent Whitchurch
2019-11-12 16:08 ` Catalin Marinas
2019-11-12 17:54 ` Linus Torvalds
2019-11-12 18:00 ` Will Deacon
2019-11-12 18:22 ` Catalin Marinas
2019-11-12 18:39 ` Linus Torvalds
2019-11-13 10:23 ` Will Deacon [this message]
2019-11-13 10:31 ` Russell King - ARM Linux admin
2019-11-13 10:49 ` Will Deacon
2019-11-14 13:28 ` Herbert Xu
2019-11-20 19:18 ` Will Deacon
2019-11-21 1:25 ` Herbert Xu
2019-11-21 16:53 ` Will Deacon
2019-11-13 16:36 ` Linus Torvalds
2019-11-13 16:40 ` Linus Torvalds
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