[PATCH] irqdomain: do not shadow nr_irqs global definition

[PATCH] irqdomain: do not shadow nr_irqs global definition

[Vincent Mailhol]

include/linux/irqnr.h declares a global variable named `nr_irqs'.

The inline function irq_domain_alloc_irqs() from
include/linux/irqdomain.h also uses the same name and thus shadow the
global declaration. Rename the function argument from `nr_irqs' to
`nbr_irqs'.

This patch silences below -Wshadow warning:

| In file included from ./arch/x86/include/asm/irqdomain.h:5,
|                  from ./arch/x86/include/asm/msi.h:5,
|                  from ./include/linux/msi.h:23,
|                  from ./include/linux/kvm_host.h:19,
|                  from arch/x86/kernel/../kvm/vmx/vmx.h:5,
|                  from arch/x86/kernel/asm-offsets.c:22:
| ./include/linux/irqdomain.h: In function 'irq_domain_alloc_irqs':
| ./include/linux/irqdomain.h:514:38: warning: declaration of 'nr_irqs' shadows a global declaration [-Wshadow]
|   514 |                         unsigned int nr_irqs, int node, void *arg)
|       |                         ~~~~~~~~~~~~~^~~~~~~
| In file included from ./include/linux/interrupt.h:10,
|                  from ./include/linux/kernel_stat.h:9,
|                  from ./include/linux/cgroup.h:26,
|                  from ./include/linux/memcontrol.h:13,
|                  from ./include/linux/swap.h:9,
|                  from ./include/linux/suspend.h:5,
|                  from arch/x86/kernel/asm-offsets.c:13:
| ./include/linux/irqnr.h:8:12: note: shadowed declaration is here
|     8 | extern int nr_irqs;
|       |            ^~~~~~~

Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
---
 include/linux/irqdomain.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index 00d577f90883..76949bb029b0 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -511,9 +511,9 @@ extern int irq_domain_activate_irq(struct irq_data *irq_data, bool early);
 extern void irq_domain_deactivate_irq(struct irq_data *irq_data);
 
 static inline int irq_domain_alloc_irqs(struct irq_domain *domain,
-			unsigned int nr_irqs, int node, void *arg)
+					unsigned int nbr_irqs, int node, void *arg)
 {
-	return __irq_domain_alloc_irqs(domain, -1, nr_irqs, node, arg, false,
+	return __irq_domain_alloc_irqs(domain, -1, nbr_irqs, node, arg, false,
 				       NULL);
 }
 
-- 
2.35.1

Re: [PATCH] irqdomain: do not shadow nr_irqs global definition

[Marc Zyngier]

On 2022-07-29 10:03, Vincent Mailhol wrote:
> include/linux/irqnr.h declares a global variable named `nr_irqs'.
> 
> The inline function irq_domain_alloc_irqs() from
> include/linux/irqdomain.h also uses the same name and thus shadow the
> global declaration. Rename the function argument from `nr_irqs' to
> `nbr_irqs'.
> 
> This patch silences below -Wshadow warning:
> 
> | In file included from ./arch/x86/include/asm/irqdomain.h:5,
> |                  from ./arch/x86/include/asm/msi.h:5,
> |                  from ./include/linux/msi.h:23,
> |                  from ./include/linux/kvm_host.h:19,
> |                  from arch/x86/kernel/../kvm/vmx/vmx.h:5,
> |                  from arch/x86/kernel/asm-offsets.c:22:
> | ./include/linux/irqdomain.h: In function 'irq_domain_alloc_irqs':
> | ./include/linux/irqdomain.h:514:38: warning: declaration of
> 'nr_irqs' shadows a global declaration [-Wshadow]
> |   514 |                         unsigned int nr_irqs, int node, void 
> *arg)
> |       |                         ~~~~~~~~~~~~~^~~~~~~
> | In file included from ./include/linux/interrupt.h:10,
> |                  from ./include/linux/kernel_stat.h:9,
> |                  from ./include/linux/cgroup.h:26,
> |                  from ./include/linux/memcontrol.h:13,
> |                  from ./include/linux/swap.h:9,
> |                  from ./include/linux/suspend.h:5,
> |                  from arch/x86/kernel/asm-offsets.c:13:
> | ./include/linux/irqnr.h:8:12: note: shadowed declaration is here
> |     8 | extern int nr_irqs;
> |       |            ^~~~~~~
> 
> Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
> ---
>  include/linux/irqdomain.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
> index 00d577f90883..76949bb029b0 100644
> --- a/include/linux/irqdomain.h
> +++ b/include/linux/irqdomain.h
> @@ -511,9 +511,9 @@ extern int irq_domain_activate_irq(struct irq_data
> *irq_data, bool early);
>  extern void irq_domain_deactivate_irq(struct irq_data *irq_data);
> 
>  static inline int irq_domain_alloc_irqs(struct irq_domain *domain,
> -			unsigned int nr_irqs, int node, void *arg)
> +					unsigned int nbr_irqs, int node, void *arg)
>  {
> -	return __irq_domain_alloc_irqs(domain, -1, nr_irqs, node, arg, false,
> +	return __irq_domain_alloc_irqs(domain, -1, nbr_irqs, node, arg, 
> false,
>  				       NULL);
>  }

I really don't think this is worth it. A function has its
own namespace, and this warning is on the long list of
"this is completely silly". Case in point:

$ git grep 'unsigned int nr_irqs'| wc -l
207

Is anything broken? Not as far as I can tell.

If there was anything to fix, it is the top-level definition
that should be more indicative of its global status. But again,
there is nothing broken so far.

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...

Re: [PATCH] irqdomain: do not shadow nr_irqs global definition

[Vincent MAILHOL]

On Fri. 29 juil. 2022 at 18:16, Marc Zyngier <maz@kernel.org> wrote:
> On 2022-07-29 10:03, Vincent Mailhol wrote:
> > include/linux/irqnr.h declares a global variable named `nr_irqs'.
> >
> > The inline function irq_domain_alloc_irqs() from
> > include/linux/irqdomain.h also uses the same name and thus shadow the
> > global declaration. Rename the function argument from `nr_irqs' to
> > `nbr_irqs'.
> >
> > This patch silences below -Wshadow warning:
> >
> > | In file included from ./arch/x86/include/asm/irqdomain.h:5,
> > |                  from ./arch/x86/include/asm/msi.h:5,
> > |                  from ./include/linux/msi.h:23,
> > |                  from ./include/linux/kvm_host.h:19,
> > |                  from arch/x86/kernel/../kvm/vmx/vmx.h:5,
> > |                  from arch/x86/kernel/asm-offsets.c:22:
> > | ./include/linux/irqdomain.h: In function 'irq_domain_alloc_irqs':
> > | ./include/linux/irqdomain.h:514:38: warning: declaration of
> > 'nr_irqs' shadows a global declaration [-Wshadow]
> > |   514 |                         unsigned int nr_irqs, int node, void
> > *arg)
> > |       |                         ~~~~~~~~~~~~~^~~~~~~
> > | In file included from ./include/linux/interrupt.h:10,
> > |                  from ./include/linux/kernel_stat.h:9,
> > |                  from ./include/linux/cgroup.h:26,
> > |                  from ./include/linux/memcontrol.h:13,
> > |                  from ./include/linux/swap.h:9,
> > |                  from ./include/linux/suspend.h:5,
> > |                  from arch/x86/kernel/asm-offsets.c:13:
> > | ./include/linux/irqnr.h:8:12: note: shadowed declaration is here
> > |     8 | extern int nr_irqs;
> > |       |            ^~~~~~~
> >
> > Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
> > ---
> >  include/linux/irqdomain.h | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
> > index 00d577f90883..76949bb029b0 100644
> > --- a/include/linux/irqdomain.h
> > +++ b/include/linux/irqdomain.h
> > @@ -511,9 +511,9 @@ extern int irq_domain_activate_irq(struct irq_data
> > *irq_data, bool early);
> >  extern void irq_domain_deactivate_irq(struct irq_data *irq_data);
> >
> >  static inline int irq_domain_alloc_irqs(struct irq_domain *domain,
> > -                     unsigned int nr_irqs, int node, void *arg)
> > +                                     unsigned int nbr_irqs, int node, void *arg)
> >  {
> > -     return __irq_domain_alloc_irqs(domain, -1, nr_irqs, node, arg, false,
> > +     return __irq_domain_alloc_irqs(domain, -1, nbr_irqs, node, arg,
> > false,
> >                                      NULL);
> >  }
>
> I really don't think this is worth it. A function has its
> own namespace, and this warning is on the long list of
> "this is completely silly". Case in point:
>
> $ git grep 'unsigned int nr_irqs'| wc -l
> 207
>
> Is anything broken? Not as far as I can tell.

Nothing is broken, my only concern is that this occurs in a header
file and thus the warning will pop up in random files which include
this header.

| git grep "unsigned int nr_irqs" include/ arch/*/include | wc -l
| 17
(and all static inline function which trigger the warning are from
linux/irqdomain.h)

Time to time, I check the W=2 output and spam from the headers makes
it annoying to triage. I absolutely do not care of shadowing
everywhere else outside of the includes directory.

> If there was anything to fix, it is the top-level definition
> that should be more indicative of its global status. But again,
> there is nothing broken so far.

This is also feasible, but it will become a tree-wide patch. And I am
quite certain that it will be NACKed right away, so I will not try
this alternate solution.


Yours sincerely,
Vincent Mailhol

Re: [PATCH] irqdomain: do not shadow nr_irqs global definition

[Vincent MAILHOL]

On Fri. 29 Jul. 2022 at 20:12, Vincent MAILHOL
<mailhol.vincent@wanadoo.fr> wrote:
> On Fri. 29 juil. 2022 at 18:16, Marc Zyngier <maz@kernel.org> wrote:
> > On 2022-07-29 10:03, Vincent Mailhol wrote:
> > > include/linux/irqnr.h declares a global variable named `nr_irqs'.
> > >
> > > The inline function irq_domain_alloc_irqs() from
> > > include/linux/irqdomain.h also uses the same name and thus shadow the
> > > global declaration. Rename the function argument from `nr_irqs' to
> > > `nbr_irqs'.
> > >
> > > This patch silences below -Wshadow warning:
> > >
> > > | In file included from ./arch/x86/include/asm/irqdomain.h:5,
> > > |                  from ./arch/x86/include/asm/msi.h:5,
> > > |                  from ./include/linux/msi.h:23,
> > > |                  from ./include/linux/kvm_host.h:19,
> > > |                  from arch/x86/kernel/../kvm/vmx/vmx.h:5,
> > > |                  from arch/x86/kernel/asm-offsets.c:22:
> > > | ./include/linux/irqdomain.h: In function 'irq_domain_alloc_irqs':
> > > | ./include/linux/irqdomain.h:514:38: warning: declaration of
> > > 'nr_irqs' shadows a global declaration [-Wshadow]
> > > |   514 |                         unsigned int nr_irqs, int node, void
> > > *arg)
> > > |       |                         ~~~~~~~~~~~~~^~~~~~~
> > > | In file included from ./include/linux/interrupt.h:10,
> > > |                  from ./include/linux/kernel_stat.h:9,
> > > |                  from ./include/linux/cgroup.h:26,
> > > |                  from ./include/linux/memcontrol.h:13,
> > > |                  from ./include/linux/swap.h:9,
> > > |                  from ./include/linux/suspend.h:5,
> > > |                  from arch/x86/kernel/asm-offsets.c:13:
> > > | ./include/linux/irqnr.h:8:12: note: shadowed declaration is here
> > > |     8 | extern int nr_irqs;
> > > |       |            ^~~~~~~
> > >
> > > Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
> > > ---
> > >  include/linux/irqdomain.h | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
> > > index 00d577f90883..76949bb029b0 100644
> > > --- a/include/linux/irqdomain.h
> > > +++ b/include/linux/irqdomain.h
> > > @@ -511,9 +511,9 @@ extern int irq_domain_activate_irq(struct irq_data
> > > *irq_data, bool early);
> > >  extern void irq_domain_deactivate_irq(struct irq_data *irq_data);
> > >
> > >  static inline int irq_domain_alloc_irqs(struct irq_domain *domain,
> > > -                     unsigned int nr_irqs, int node, void *arg)
> > > +                                     unsigned int nbr_irqs, int node, void *arg)
> > >  {
> > > -     return __irq_domain_alloc_irqs(domain, -1, nr_irqs, node, arg, false,
> > > +     return __irq_domain_alloc_irqs(domain, -1, nbr_irqs, node, arg,
> > > false,
> > >                                      NULL);
> > >  }
> >
> > I really don't think this is worth it. A function has its
> > own namespace, and this warning is on the long list of
> > "this is completely silly". Case in point:
> >
> > $ git grep 'unsigned int nr_irqs'| wc -l
> > 207
> >
> > Is anything broken? Not as far as I can tell.
>
> Nothing is broken, my only concern is that this occurs in a header
> file and thus the warning will pop up in random files which include
> this header.
>
> | git grep "unsigned int nr_irqs" include/ arch/*/include | wc -l
> | 17
> (and all static inline function which trigger the warning are from
> linux/irqdomain.h)
>
> Time to time, I check the W=2 output and spam from the headers makes
> it annoying to triage. I absolutely do not care of shadowing
> everywhere else outside of the includes directory.
>
> > If there was anything to fix, it is the top-level definition
> > that should be more indicative of its global status. But again,
> > there is nothing broken so far.
>
> This is also feasible, but it will become a tree-wide patch. And I am
> quite certain that it will be NACKed right away, so I will not try
> this alternate solution.

To add some figures, on a "make allyesconfig" (linux-next branch,
x86_64 build, gcc 12), there are in total 36005 -Wshadow and
irqdomain.h accounts for 7094 of all these (i.e. this patch suppresses
roughly one fifth of all -Wshadow warnings tree wide).


Yours sincerely,
Vincent Mailhol