On Fri, Oct 14, 2022 at 7:26 AM Alexander Gordeev
<agordeev@xxxxxxxxxxxxx> wrote:
>
> Commit 78e5a3399421 ("cpumask: fix checking valid cpu range") has
> started issuing warnings when reading /proc/cpuinfo and config
> DEBUG_PER_CPU_MAPS is enabled. Avoid calling cpumask_next() with
> the cpu index equal to nr_cpu_ids - 1 and ensure no warning is
> generated.
>
> Link: https://lore.kernel.org/r/20221012081905.1800640-1-ajones@xxxxxxxxxxxxxxxx
> Reported-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
> Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
> ---
> arch/s390/kernel/processor.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/s390/kernel/processor.c b/arch/s390/kernel/processor.c
> index a194611ba88c..908a0be900ea 100644
> --- a/arch/s390/kernel/processor.c
> +++ b/arch/s390/kernel/processor.c
> @@ -334,6 +334,8 @@ static int show_cpuinfo(struct seq_file *m, void *v)
>
> static inline void *c_update(loff_t *pos)
> {
> + if (*pos >= nr_cpu_ids)
> + return NULL;
> if (*pos)
> *pos = cpumask_next(*pos - 1, cpu_online_mask);
> else
This silences the warning entirely. If you don't need it, I'd suggest
using find_next_bit()
instead. But from the discussion to similar patch, I think you need to
allow nr_cpu_ids
only:
+ if (*pos == nr_cpu_ids)
+ return NULL;
