From: Jamie Lokier <jamie@shareable.org>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Tony Lindgren <tony@atomide.com>,
linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 3/3] ARM: Select CPU_32v6K for CPU_V7 only if ARCH_OMAP2 isnot selected
Date: Thu, 28 Jan 2010 18:33:03 +0000 [thread overview]
Message-ID: <20100128183303.GA30029@shareable.org> (raw)
In-Reply-To: <1264701931.7064.98.camel@pc1117.cambridge.arm.com>
Catalin Marinas wrote:
> > Hmm, but then we can't compile in SMP for single core systems and
> > keep it bootable on single core v6?
>
> Not with the current kernel since it hardcodes the shareability bit in
> the page tables and the LDREX/STREX operations don't work as expected on
> uniprocessor hardware.
My understanding of LDREX/STREX is that it's allowed to be quite
different on uniprocessors (and CPU-local activity on SMP), but if
it's used properly it still works ok.
Can you say a bit more about assumptions made by the kernel using
LDREX/STREX that fail on uniprocessor hardware?
Is it just the shareability bit in page tables having the wrong value?
Thanks,
-- Jamie
WARNING: multiple messages have this Message-ID (diff)
From: jamie@shareable.org (Jamie Lokier)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 3/3] ARM: Select CPU_32v6K for CPU_V7 only if ARCH_OMAP2 isnot selected
Date: Thu, 28 Jan 2010 18:33:03 +0000 [thread overview]
Message-ID: <20100128183303.GA30029@shareable.org> (raw)
In-Reply-To: <1264701931.7064.98.camel@pc1117.cambridge.arm.com>
Catalin Marinas wrote:
> > Hmm, but then we can't compile in SMP for single core systems and
> > keep it bootable on single core v6?
>
> Not with the current kernel since it hardcodes the shareability bit in
> the page tables and the LDREX/STREX operations don't work as expected on
> uniprocessor hardware.
My understanding of LDREX/STREX is that it's allowed to be quite
different on uniprocessors (and CPU-local activity on SMP), but if
it's used properly it still works ok.
Can you say a bit more about assumptions made by the kernel using
LDREX/STREX that fail on uniprocessor hardware?
Is it just the shareability bit in page tables having the wrong value?
Thanks,
-- Jamie
next prev parent reply other threads:[~2010-01-28 18:33 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-26 19:37 [PATCH 0/3] Add tmp register for debug-macro.S, do not select CPU_32v6K for omap2 Tony Lindgren
2010-01-26 19:37 ` Tony Lindgren
2010-01-26 19:37 ` [PATCH 1/3] ARM: Add tmp register for addruart and loadsp Tony Lindgren
2010-01-26 19:37 ` Tony Lindgren
2010-01-26 19:37 ` [PATCH 2/3] ARM: Add tmp register for debug-macro.S files Tony Lindgren
2010-01-26 19:37 ` Tony Lindgren
2010-01-26 19:37 ` [PATCH 3/3] ARM: Select CPU_32v6K for CPU_V7 only if ARCH_OMAP2 is not selected Tony Lindgren
2010-01-26 19:37 ` Tony Lindgren
2010-01-28 11:00 ` [PATCH 3/3] ARM: Select CPU_32v6K for CPU_V7 only if ARCH_OMAP2 isnot selected Catalin Marinas
2010-01-28 11:00 ` Catalin Marinas
2010-01-28 17:47 ` Tony Lindgren
2010-01-28 17:47 ` Tony Lindgren
2010-01-28 18:05 ` Catalin Marinas
2010-01-28 18:05 ` Catalin Marinas
2010-01-28 18:33 ` Jamie Lokier [this message]
2010-01-28 18:33 ` Jamie Lokier
2010-01-29 10:38 ` Catalin Marinas
2010-01-29 10:38 ` Catalin Marinas
2010-01-29 10:42 ` Catalin Marinas
2010-01-29 10:42 ` Catalin Marinas
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