Re: Observations on LLSC and SMP

[Daniel Jacobowitz <dan@debian.org>]

On Fri, Mar 25, 2005 at 11:24:05AM -0800, Ed Martini wrote:
> 1. If the first part of the if were an ifdef instead it would result in 
> a code size reduction as well as a runtime performance gain.

You should spend a little time playing with an optimizing compiler. 
They're capable of working out when a condition will always be false.

> 2. In atomic.h the "C lang stuff" is wrapped with a spinlock.  In the 
> SMP case the spinlock will result in code that contains ll and sc 
> instructions, so I infer that there are no SMP system configs that use 
> CPUs that don't have the ll and sc instructions. 

That's correct.  It is not practical to implement SMP without a mutex
primitive.


-- 
Daniel Jacobowitz
CodeSourcery, LLC