On Sun, Mar 19, 2006 at 11:33:17AM -0800, Linus Torvalds wrote:
> Of course, I shouldn't say "works", since it is still totally untested. It
> _looks_ good, and that statement expression usage is just _so_ ugly it's
> cute.
>
> Linus
At least, you could have moved the macro closer to where it's used.
It's very uncommon to break a statement within an if condition, and
it's not expected that the macro you're calling does a break under
you. It took me several minutes to understand precisely how this
works. Now it seems trivial, but I guess that at 3am I would have
gone to bed instead.
One first enhancement would be to make it easier to understand
by putting it closer to its user :
#elif NR_CPUS > 1
#define check_for_each_cpu(cpu, mask) \
({ unsigned long __bits = (mask).bits[0] >> (cpu); if (!__bits) break; __bits & 1; })
#define for_each_cpu_mask(cpu, mask) \
for ((cpu) = 0; (cpu) < NR_CPUS; (cpu)++) \
if (!check_for_each_cpu(cpu, mask)) \
continue; \
else
Now, does removing the macro completely change the output code ?
I think that if something written like this produces the same
code, it would be easier to read :
#define for_each_cpu_mask(cpu, mask) \
for ((cpu) = 0; (cpu) < NR_CPUS; (cpu)++) { \
unsigned long __bits = (mask).bits[0] >> (cpu); \
if (!__bits) \
break; \
if (!__bits & 1) \
continue; \
else
Regards,
Willy
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