Re: [regression] sched_getaffinity fails with EINVAL in 2.6.31-rc4

Rusty Russell
2009-07-29T01:49:00Z

On Tue, 28 Jul 2009 03:42:15 am David Rientjes wrote:
> On Mon, 27 Jul 2009, Gregory Haskins wrote:
>
> > I am not sure when this started, but noticed that sched_getaffinity is
> > not working in -rc4.
> >
> > [pid 6254] sched_getaffinity(0, 128, 0x7f80586b1fe0) = -1 EINVAL
> > (Invalid argument)
> >
> > Here is a simple program for reproduction:
> >
> > #include <sched.h>
> >
> > int main(void)
> > {
> > cpu_set_t mask;
> > int ret;
> >
> > ret = sched_getaffinity(0, sizeof(mask), &mask);
> > if (ret < 0)
> > perror("getaffinity");
> >
> > return ret;
> > }
> >
> > If I get time, I will bisect this later today.
> >
>
> It's most likely due to the cpumask changes. I don't know what cpu_set_t
> is, but it's probably smaller than CONFIG_NR_CPUS rounded up to a multiple
> of sizeof(long).

It's simply that you finally ran this on a kernel which had
CONFIG_NR_CPUS > 1024.

I argued strongly against the set and getaffinity interfaces when they were
introduced; they can't be used in general without a loop (enlarge cpu_set,
retry).

Cheers,
Rusty.