Mathieu Desnoyers writes:
> +static __inline__ int local_dec_if_positive(local_t *l)
> +{
> + int t;
> +
> + __asm__ __volatile__(
> +"1: lwarx %0,0,%1 # local_dec_if_positive\n\
> + addic. %0,%0,-1\n\
> + blt- 2f\n"
> + PPC405_ERR77(0,%1)
> +" stwcx. %0,0,%1\n\
> + bne- 1b"
This has the same bugs that we fixed recently in atomic_dec_if_positive;
first, on 64-bit machines, the lwarx will zero-extend the word loaded
from memory, and so the result of the addic will be negative only if
the word was originally 0. Secondly, even on 32-bit machines,
0x80000000 will be considered positive since decrementing it gives
0x7fffffff, which is positive.
> +/* Use these for per-cpu local_t variables: on some archs they are
> + * much more efficient than these naive implementations. Note they take
> + * a variable, not an address.
> + *
> + * This could be done better if we moved the per cpu data directly
> + * after GS.
> + */
What's "GS"? Does this comment really apply on powerpc?
Paul.
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