* barriers in mutexes?
@ 2011-02-03 2:05 Steve Muckle
2011-02-03 11:08 ` Russell King - ARM Linux
0 siblings, 1 reply; 4+ messages in thread
From: Steve Muckle @ 2011-02-03 2:05 UTC (permalink / raw)
To: linux-arm-kernel
Hello,
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?
thanks,
Steve
--
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
^ permalink raw reply [flat|nested] 4+ messages in thread
* barriers in mutexes?
2011-02-03 2:05 barriers in mutexes? Steve Muckle
@ 2011-02-03 11:08 ` Russell King - ARM Linux
2011-02-03 16:56 ` Steve Muckle
0 siblings, 1 reply; 4+ messages in thread
From: Russell King - ARM Linux @ 2011-02-03 11:08 UTC (permalink / raw)
To: linux-arm-kernel
On Wed, Feb 02, 2011 at 06:05:46PM -0800, Steve Muckle wrote:
> Hello,
>
> 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)
^ permalink raw reply [flat|nested] 4+ messages in thread
* barriers in mutexes?
2011-02-03 11:08 ` Russell King - ARM Linux
@ 2011-02-03 16:56 ` Steve Muckle
2011-02-20 13:14 ` Russell King - ARM Linux
0 siblings, 1 reply; 4+ messages in thread
From: Steve Muckle @ 2011-02-03 16:56 UTC (permalink / raw)
To: linux-arm-kernel
On 02/03/11 03:08, Russell King - ARM Linux wrote:
> On Wed, Feb 02, 2011 at 06:05:46PM -0800, Steve Muckle wrote:
>> 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
--
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
^ permalink raw reply [flat|nested] 4+ messages in thread
* barriers in mutexes?
2011-02-03 16:56 ` Steve Muckle
@ 2011-02-20 13:14 ` Russell King - ARM Linux
0 siblings, 0 replies; 4+ messages in thread
From: Russell King - ARM Linux @ 2011-02-20 13:14 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Feb 03, 2011 at 08:56:15AM -0800, Steve Muckle wrote:
> On 02/03/11 03:08, Russell King - ARM Linux wrote:
> > On Wed, Feb 02, 2011 at 06:05:46PM -0800, Steve Muckle wrote:
> >> 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.
Patch welcome.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2011-02-03 2:05 barriers in mutexes? Steve Muckle
2011-02-03 11:08 ` Russell King - ARM Linux
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2011-02-20 13:14 ` Russell King - ARM Linux
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