Messages in this thread | | | From | Vincent MAILHOL <> | Date | Sat, 30 Jul 2022 13:26:21 +0900 | Subject | Re: [PATCH] irqdomain: do not shadow nr_irqs global definition |
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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
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