Re: where is __memory_barrier in kernel ?

[piyush moghe <pmkernel@xxxxxxxxx>]

Yes what you are saying is also right, since in order to prevent the ordering all the pending memory operations should have completed

hence as you mentioned processor stops and make sure all the memory operations are completed.

On Tue, Mar 8, 2011 at 11:59 AM, Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx> wrote:

On Sun, Mar 6, 2011 at 21:02, loody <miloody@xxxxxxxxx> wrote:
> hi all:
> I grep kernel source and found cpu_relax is defined as
> __memory_barrier(), which seems not defined in kernel source.
> At beginning I think it may be the gcc build-in functions, but I
> cannot find in the gcc document.
> Where and what is that used for?

Hi..

are you sure it's memory barrier? I check the source in lxr.linux.no
(2.6.37.3) and cpu_relax is expanded as 'rep' and 'nop' asm
instruction

but speaking about __memory_barrier(), I find it in
http://lxr.linux.no/#linux+v2.6.37.3/include/linux/compiler-intel.h#L19...meaning...(at
least for me), it's a macro specificly defined in Intel C compiler
(not gcc which we usually uses).

IMHO, it does the same as barrier everywhere....processor stop a while
and it make sure any memory operation (especially write) has been
done....

--
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com

_______________________________________________
Kernelnewbies mailing list
Kernelnewbies@xxxxxxxxxxxxxxxxx
http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

_______________________________________________
Kernelnewbies mailing list
Kernelnewbies@xxxxxxxxxxxxxxxxx
http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies