barriers in mutexes?

On 02/03/11 03:08, Russell King - ARM Linux wrote:

On Wed, Feb 02, 2011 at 06:05:46PM -0800, Steve Muckle wrote:

quoted

Looking at kernel/mutex.c and arch/arm/include/asm/mutex.h, it appears
there aren't any memory barriers in the fast path of mutexes. I see this
was discussed here a long time back:

http://patchwork.kernel.org/patch/25856/

How was this resolved?

bac4e96 ([ARM] barriers: improve xchg, bitops and atomic SMP barriers)

The fast path of mutexes on ARM >= v6 doesn't seem to use these
operations - it's just ldrex/strex. Looking at the v7 ARM ARM it seems
barriers are still required with ldrex/strex.

thanks,
Steve

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