Messages in this thread | | | Date | Fri, 20 Apr 2018 18:51:39 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched/fair: Change sched_feat(x) in !CONFIG_SCHED_DEBUG case |
| |
On Fri, Apr 20, 2018 at 06:29:07PM +0200, Philipp Klocke wrote: > The gain is stopping a warning that clutters the output log of clang.
Well, you should not be using clang anyway. It is known to miscompile the kernel.
> To improve readability, one can drop the ifdef-structure and just keep > the right shift version, like Nicholas suggested. This will have a (very > small) > impact on performance in CONFIG_SCHED_DEBUG case, but when > debugging, performance is no problem anyways.
See that is two bad choices.
> > Also, if sysctl_sched_features is a constant, the both expressions > > _should_ really result in a constant and clang should still warn about > > it. > No, because clang only warns if the constant is neither 1 nor 0. > (These being the 'best' integer representations of booleans)
Then won't something like so work?
#define sched_feat(x) !!(sysctl_sched_features & (1UL << __SCHED_FEAT_##x))
That forces it into _Bool space (0/1) and per the above rule will no longer warn.
| |