[Prism54-devel] wmb - smp_wmp

[Jens Maurer]

Margit Schubert-While wrote:
> Kernel question:
> http://marc.theaimsgroup.com/?l=linux-kernel&m=108764360920610&w=2 
> <http://marc.theaimsgroup.com/?l=linux-kernel&m=108764360920610&w=2>

Here's a comment from the Linux 2.6.7 source, include/asm-ppc64/system.h

  * For wmb(), we use sync since wmb is used in drivers to order
  * stores to system memory with respect to writes to the device.
  * However, smp_wmb() can be a lighter-weight eieio barrier on
  * SMP since it is only used to order updates to system memory.

As far as I am aware, we only have the "write to device" case
in the driver (i.e. wmb(), not smp_wmb()).  For synchronizing
different CPUs, we mostly use spinlocks.

Jens Maurer