On Sat, 18 Aug 2007, Satyam Sharma wrote:
>
> No code does (or would do, or should do):
>
> x.counter++;
>
> on an "atomic_t x;" anyway.
That's just an example of a general problem.
No, you don't use "x.counter++". But you *do* use
if (atomic_read(&x) <= 1)
and loading into a register is stupid and pointless, when you could just
do it as a regular memory-operand to the cmp instruction.
And as far as the compiler is concerned, the problem is the 100% same:
combining operations with the volatile memop.
The fact is, a compiler that thinks that
movl mem,reg
cmpl $val,reg
is any better than
cmpl $val,mem
is just not a very good compiler. But when talking about "volatile",
that's exactly what ytou always get (and always have gotten - this is
not a regression, and I doubt gcc is alone in this).
Linus
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