Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures

[Arjan van de Ven <arjan@infradead.org>]

On Fri, 2007-08-17 at 12:50 -0600, Chris Friesen wrote:
> Linus Torvalds wrote:
> 
> >  - in other words, the *only* possible meaning for "volatile" is a purely 
> >    single-CPU meaning. And if you only have a single CPU involved in the 
> >    process, the "volatile" is by definition pointless (because even 
> >    without a volatile, the compiler is required to make the C code appear 
> >    consistent as far as a single CPU is concerned).
> 
> I assume you mean "except for IO-related code and 'random' values like 
> jiffies" as you mention later on?  I assume other values set in 
> interrupt handlers would count as "random" from a volatility perspective?
> 
> > So anybody who argues for "volatile" fixing bugs is fundamentally 
> > incorrect. It does NO SUCH THING. By arguing that, such people only show 
> > that you have no idea what they are talking about.
> 
> What about reading values modified in interrupt handlers, as in your 
> "random" case?  Or is this a bug where the user of atomic_read() is 
> invalidly expecting a read each time it is called?

the interrupt handler case is an SMP case since you do not know
beforehand what cpu your interrupt handler will run on.