From: Esben Nielsen <nielsen.esben@gogglemail.com>
To: Liu Dave-r63238 <DaveLiu@freescale.com>
Cc: Esben Nielsen <nielsen.esben@gogglemail.com>,
Xupei Liang <tliang@yahoo.com>,
linuxppc-embedded@ozlabs.org
Subject: RE: atomic operations in user space
Date: Tue, 29 Aug 2006 11:56:30 +0200 (CEST) [thread overview]
Message-ID: <Pine.LNX.4.64.0608291136370.12461@frodo.shire> (raw)
In-Reply-To: <995B09A8299C2C44B59866F6391D263511BAE8@zch01exm21.fsl.freescale.net>
On Tue, 29 Aug 2006, Liu Dave-r63238 wrote:
>>> 2) These mutexes are based on futexes which requires atomic
>>> operations in userspace. These are available on most architectures.
> Look at
>>> the glibc code in
>>> nptl/sysdeps/unix/sysv/linux/powerpc/lowlevellock.h for instance.
>>> Use that and your PPC manual to implement your atomic operations.
>>
>> No matter semaphore or futex, it uses system calls to kernel.
There is only a system call if there is congestion - that is the whole idea
behind the futex.
>> And the
>> true atomic operation is in kernel not user space.
"True" atomic operations are available in user space on most architectures.
>> Maybe
>> it's feasible
>> for other architectures to do atomic operations directly in
>> user space.
>> IMHO, not for powerpc.
It is available for PowerPC, but not in POWER and POWER2 instructionsets
according to http://www.nersc.gov/vendor_docs/ibm/asm/lwarx.htm#idx607
It is the same in the ARM world: Atomic instructions was introduced in
ARMv6 I believe. Older ARM processors don't have them.
>
> Are you meaning that we didn't do atomic operations directly in user
> space
> on powerpc platform ?
>
Well, that is not the conclusion I get either when reading the glibc code.
Try to look at glibc-2.3.5/sysdeps/powerpc/bits/atomic.h.
This is by the way probably what the original post in this thread wanted
in the first place!
Esben
> -DAve
> _______________________________________________
> Linuxppc-embedded mailing list
> Linuxppc-embedded@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-embedded
>
next prev parent reply other threads:[~2006-08-29 9:59 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-08-29 0:43 atomic operations in user space Xupei Liang
2006-08-29 6:43 ` Li Yang-r58472
2006-08-29 8:33 ` Esben Nielsen
2006-08-29 8:54 ` Li Yang-r58472
2006-08-29 9:20 ` Liu Dave-r63238
2006-08-29 9:56 ` Esben Nielsen [this message]
2006-08-29 10:05 ` Liu Dave-r63238
2006-08-29 10:52 ` Li Yang-r58472
2006-08-29 11:26 ` Esben Nielsen
2006-08-29 11:30 ` Esben Nielsen
2006-08-29 12:36 ` Brent Cook
-- strict thread matches above, loose matches on Subject: below --
2006-08-30 2:17 Liu Dave-r63238
2006-08-30 2:27 ` Liu Dave-r63238
2006-08-30 2:40 ` Li Yang-r58472
2006-08-29 13:37 Li Yang
2006-08-29 16:05 ` Esben Nielsen
2006-08-29 17:00 ` Li Yang
2006-08-23 19:03 Terry Liang
2006-08-24 10:39 ` Li Yang-r58472
2006-08-24 14:18 ` Brent Cook
2006-08-25 2:33 ` Li Yang-r58472
2006-08-22 20:50 Xupei Liang
2006-08-22 22:23 ` Arnd Bergmann
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