Re: [PATCH v3] ARM64: Dynamically allocate cpumasks and increase supported CPUs to 512

[Catalin Marinas <catalin.marinas@arm.com>]

On Mon, Mar 11, 2024 at 05:51:04PM +0100, Marek Szyprowski wrote:
> On 11.03.2024 16:22, Catalin Marinas wrote:
> > On Mon, Mar 11, 2024 at 03:56:37PM +0100, Marek Szyprowski wrote:
> >> On 11.03.2024 13:12, Mark Rutland wrote:
> >>> On Fri, Mar 08, 2024 at 09:08:59AM -0800, Christoph Lameter (Ampere) wrote:
> >>>> On Fri, 8 Mar 2024, Marek Szyprowski wrote:
> >>>>>>> It looks that cpufreq-dt and/or opp drivers needs some adjustments
> >>>>>>> related with this change.
> >>>>>> That's strange. Is this with defconfig? I wonder whether NR_CPUS being
> >>>>>> larger caused the issue with this specific code. Otherwise
> >>>>>> CPUMASK_OFFSTACK may not work that well on arm64.
> >>>> cpumask handling must use the accessor functions provided in
> >>>> include/linux/cpumask.h for declaring and accessing cpumasks. It is likely
> >>>> related to the driver opencoding one of the accessors.
> >>> I took a look at both the OPP code and the cpufreq-dt code and it looks like
> >>> those are doign the right thing w.r.t. cpumask manipulation (i.e. they only use
> >>> the cpumask accessors, and use the cpumask_var_*() functions to dynamically
> >>> allocate/free cpumasks). Maybe I've missed something, but superficially those
> >>> look right.
> >>>
> >>> Marek, can you try reverting this commit and trying defconfig + NR_CPUS=512?
> >> Yes, with $subject reverted and CONFIG_NR_CPUS=512 everything works
> >> fine, so it must be something else broken.
> > Thanks for confirming. Would you mind testing the problematic commit
> > with CONFIG_DEBUG_PER_CPU_MAPS enabled? If it doesn't show anything
> > obvious that can be fixed quickly, I'll revert the commit and queue it
> > again after -rc1 for 6.10 (I haven't sent 6.9 the pull request yet).
> 
> I've enabled this option, but unfortunately it didn't reveal anything 
> more besides the warning and error I've posted in my initial report. I 
> will try to analyze this issue further, but I won't manage to do this today.

No worries, thanks for giving this a try.

-- 
Catalin