Re: [PATCH RESEND 1/1] lib/Kconfig: remove DEBUG_PER_CPU_MAPS dependency for CPUMASK_OFFSTACK

[Libo Chen]

On 4/12/22 19:13, Randy Dunlap wrote:
> Hi,
>
> On 4/12/22 18:35, Libo Chen wrote:
> > Hi Randy,
> >
> > On 4/12/22 17:18, Randy Dunlap wrote:
> > > Hi--
> > >
> > > On 4/12/22 16:15, Libo Chen wrote:
> > > > Forcing CPUMASK_OFFSTACK to be conditoned on DEBUG_PER_CPU_MAPS doesn't
> > > > make a lot of sense nowaday. Even the original patch dating back to 2008,
> > > > aab46da0520a ("cpumask: Add CONFIG_CPUMASK_OFFSTACK") didn't give any
> > > > rationale for such dependency.
> > > >
> > > > Nowhere in the code supports the presumption that DEBUG_PER_CPU_MAPS is
> > > > necessary for CONFIG_CPUMASK_OFFSTACK. Make no mistake, it's good to
> > > > have DEBUG_PER_CPU_MAPS for debugging purpose or precaution, but it's
> > > > simply not a hard requirement for CPUMASK_OFFSTACK. Moreover, x86 Kconfig
> > > > already can set CPUMASK_OFFSTACK=y without DEBUG_PER_CPU_MAPS=y.
> > > > There is no reason other architectures cannot given the fact that they
> > > > have even fewer, if any, arch-specific CONFIG_DEBUG_PER_CPU_MAPS code than
> > > > x86.
> > > >
> > > > Signed-off-by: Libo Chen <libo.chen@xxxxxxxxxx>
> > > > ---
> > > >    lib/Kconfig | 2 +-
> > > >    1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/lib/Kconfig b/lib/Kconfig
> > > > index 087e06b4cdfd..7209039dfb59 100644
> > > > --- a/lib/Kconfig
> > > > +++ b/lib/Kconfig
> > > > @@ -511,7 +511,7 @@ config CHECK_SIGNATURE
> > > >        bool
> > > >      config CPUMASK_OFFSTACK
> > > > -    bool "Force CPU masks off stack" if DEBUG_PER_CPU_MAPS
> > > This "if" dependency only controls whether the Kconfig symbol's prompt is
> > > displayed (presented) in kconfig tools. Removing it makes the prompt always
> > > be displayed.
> > >
> > > Any architecture could select (should be able to) CPUMASK_OFFSTACK independently
> > > of DEBUG_PER_CPU_MAPS.
> > Do you mean changing arch/xxxx/Kconfig to select CPUMASK_OFFSTACK under some config xxx? That will work but it requires code changes for each architecture.
> > But if you are talking about setting CONFIG_CPUMASK_OFFSTACK=y without CONFIG_DEBUG_PER_CPU_MAPS directly in config file, I have tried, it doesn't work.
> I'm just talking about the Kconfig change below.  Not talking about whatever else
> it might require per architecture.
>
> But you say you have tried that and it doesn't work. What part of it doesn't work?
> The Kconfig part or some code execution?
oh the Kconfig part. For example, make olddefconfig on a config file 
with CPUMASK_OFFSTACK=y only turns off CPUMASK_OFFSTACK unless I 
explicitly set DEBUG_PER_CPU_MAPS=y

Libo
> I'll test the Kconfig part of it later (in a few hours).
>
> > Libo
> > > Is there another problem here?
> > >
> > > > +    bool "Force CPU masks off stack"
> > > >        help
> > > >          Use dynamic allocation for cpumask_var_t, instead of putting
> > > >          them on the stack.  This is a bit more expensive, but avoids