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SubjectRe: kprobes: get rid of distinct type warning
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On Tue, 5 Jan 2010 02:27:02 am Heiko Carstens wrote:
> On Wed, Dec 30, 2009 at 01:29:45PM -0800, Andrew Morton wrote:
> > On Mon, 21 Dec 2009 13:02:24 +0100
> > Heiko Carstens <heiko.carstens@de.ibm.com> wrote:
> >
> > > Of course the patch wouldn't help for CONFIG_PREEMPT and !CONFIG_SMP since
> > > we would have a comparison of a signed and and unsigned value again *sigh*.
> >
> > We should fix that, shouldn't we? Rather than working around it at one
> > caller site.
> >
> > : #if NR_CPUS > 1
> > : #define num_online_cpus() cpumask_weight(cpu_online_mask)
> > : #define num_possible_cpus() cpumask_weight(cpu_possible_mask)
> > : #define num_present_cpus() cpumask_weight(cpu_present_mask)
> > : #define num_active_cpus() cpumask_weight(cpu_active_mask)
> > : #define cpu_online(cpu) cpumask_test_cpu((cpu), cpu_online_mask)
> > : #define cpu_possible(cpu) cpumask_test_cpu((cpu), cpu_possible_mask)
> > : #define cpu_present(cpu) cpumask_test_cpu((cpu), cpu_present_mask)
> > : #define cpu_active(cpu) cpumask_test_cpu((cpu), cpu_active_mask)
> > : #else
> > : #define num_online_cpus() 1
> > : #define num_possible_cpus() 1
> > : #define num_present_cpus() 1
> > : #define num_active_cpus() 1
> > : #define cpu_online(cpu) ((cpu) == 0)
> > : #define cpu_possible(cpu) ((cpu) == 0)
> > : #define cpu_present(cpu) ((cpu) == 0)
> > : #define cpu_active(cpu) ((cpu) == 0)
> > : #endif
> >
> > The num_*() "functions" return unsigned on SMP and int on UP. This is
> > wrong.
> >
> > The cpu_*() "functions" got lucky and return int in both cases.
> >
> > Personally I think it's neatest if a quantity which can never be
> > negative is held in an unsigned type. Than includes anything starting
> > with "num". But for expediency's sake we could live with making these
> > things consistently return "int".
> >
> > Alas, changing those four num_*() "functions" to return int on SMP is a
> > pretty wide-reaching change and will probably expose warts.
>
> Looks like there are quite a lot of num_* function usages in the kernel.
> Some seem to assume they return an int some assume an unsigned int.
> Don't know if it's worth changing anything here.
> Maybe Rusty has an opinion.

If we have to go one way or the other, go with unsigned.

What does such a patch look like?

Thanks,
Rusty.


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