On Wed, 8 Aug 2007 21:18:25 -0700 (PDT)
Linus Torvalds <[email protected]> wrote:
>
>
> On Wed, 8 Aug 2007, Chris Snook wrote:
> >
> > Some architectures currently do not declare the contents of an atomic_t to be
> > volatile. This causes confusion since atomic_read() might not actually read
> > anything if an optimizing compiler re-uses a value stored in a register, which
> > can break code that loops until something external changes the value of an
> > atomic_t.
>
> I'd be *much* happier with "atomic_read()" doing the "volatile" instead.
>
> The fact is, volatile on data structures is a bug. It's a wart in the C
> language. It shouldn't be used.
Why? It's a wart! Is it due to unclear C standard on volatile related point?
Why the *volatile-accesses-in-code* is acceptable, does C standard make it clear?
-- Jerry
>
> Volatile accesses in *code* can be ok, and if we have "atomic_read()"
> expand to a "*(volatile int *)&(x)->value", then I'd be ok with that.
>
> But marking data structures volatile just makes the compiler screw up
> totally, and makes code for initialization sequences etc much worse.
>
> Linus
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