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

[Segher Boessenkool]

> > > Part of the motivation here is to fix heisenbugs.  If I knew where 
> > > they
> >
> > By the same token we should probably disable optimisations
> > altogether since that too can create heisenbugs.
>
> Precisely the point -- use of volatile (whether in casts or on asms)
> in these cases are intended to disable those optimizations likely to
> result in heisenbugs.

The only thing volatile on an asm does is create a side effect
on the asm statement; in effect, it tells the compiler "do not
remove this asm even if you don't need any of its outputs".

It's not disabling optimisation likely to result in bugs,
heisen- or otherwise; _not_ putting the volatile on an asm
that needs it simply _is_ a bug :-)


Segher

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