From: jamie@shareable.org (Jamie Lokier)
To: linux-arm-kernel@lists.infradead.org
Subject: __xchg for sizes other than 32bit
Date: Wed, 10 Mar 2010 23:16:26 +0000 [thread overview]
Message-ID: <20100310231626.GB11663@shareable.org> (raw)
In-Reply-To: <20100310173503.GC12345@n2100.arm.linux.org.uk>
Russell King - ARM Linux wrote:
> On Wed, Mar 10, 2010 at 06:22:21PM +0200, Imre Deak wrote:
> > recently you've added support for __cmpxchg for ARMv6+. There the assumption
> > is that ldrex[bh]/strex[bh] is only supported on platforms with the 32v6K
> > extension.
> >
> > Currently the __xchg code uses these even without the extension. Should this
> > be fixed?
>
> >From what I remember, the half-word versions definitely aren't supported
> on anything without V6K extensions. I think that the byte and word
> versions are supported on V6 and up though.
>
> That'd make both __cmpxchg and __xchg slightly buggy, in different ways.
>
> What it does mean is that atomic operations on unsigned shorts using
> ldrex/strex will only be possible on V6K and up.
It's possible to emulate 16-bit cmpxchg using 32-bit cmpxchg.
xchg can't be emulated with wider xchg, but of course it can use wider
cmpxchg in a loop.
That sort of thing probably should be in asm-generic somewhere.
-- Jamie
next prev parent reply other threads:[~2010-03-10 23:16 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-10 16:22 __xchg for sizes other than 32bit Imre Deak
2010-03-10 17:35 ` Russell King - ARM Linux
2010-03-10 20:02 ` [PATCH] ARM support single byte cmpxchg and cmpxchg_local on ARMv6 Mathieu Desnoyers
2010-03-10 20:30 ` Russell King - ARM Linux
2010-03-10 21:15 ` Mathieu Desnoyers
2010-03-10 23:16 ` Jamie Lokier [this message]
2010-03-18 9:29 ` [PATCH 1/1] [RFC] arm: add half-word __xchg Alexander Shishkin
2010-03-18 12:32 ` Mathieu Desnoyers
2010-03-18 12:37 ` Alexander Shishkin
2010-03-18 13:33 ` Alexander Shishkin
2010-03-18 13:50 ` Mathieu Desnoyers
2010-03-18 16:33 ` Imre Deak
2010-03-18 17:21 ` Mathieu Desnoyers
2010-03-18 19:00 ` Imre Deak
2010-03-18 19:30 ` Mathieu Desnoyers
2010-03-19 1:49 ` Jamie Lokier
2010-03-19 2:12 ` Mathieu Desnoyers
2010-03-19 3:36 ` Jamie Lokier
2010-03-25 15:52 ` [PATCH 1/1] [RFCv2] " Alexander Shishkin
2010-03-25 16:42 ` Alexander Shishkin
2010-03-27 22:52 ` Russell King - ARM Linux
2010-03-28 0:14 ` Jamie Lokier
2010-03-28 0:18 ` Russell King - ARM Linux
2010-03-28 1:00 ` Mathieu Desnoyers
2010-03-28 14:39 ` Jamie Lokier
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