Re: [PATCH] mm/memprofiling: explicitly include irqflags.h in alloc_tag.h

[Klara Modin]

On 2024-04-07 19:01, Kent Overstreet wrote:
> On Sun, Apr 07, 2024 at 03:32:52PM +0200, Klara Modin wrote:
> > linux/alloc_tag.h uses the macro this_cpu_inc which eventually expands to:
> >
> >   #define this_cpu_generic_to_op(pcp, val, op)				\
> >   do {									\
> >   	unsigned long __flags;						\
> >   	raw_local_irq_save(__flags);					\
> >   	raw_cpu_generic_to_op(pcp, val, op);				\
> >   	raw_local_irq_restore(__flags);					\
> >   } while (0)
> >
> > The macros raw_local_irq_save and raw_local_irq_restore are defined in
> > linux/irqflags.h which is not included implicitly on all configs.
> > Therefore, include it explicitly.
> >
> > Fixes: ac906a377c67 ("lib: add allocation tagging support for memory allocation profiling")
> > Link: https://lore.kernel.org/lkml/6b8149f3-80e6-413c-abcb-1925ecda9d8c@xxxxxxxxx/
> > Signed-off-by: Klara Modin <klarasmodin@xxxxxxxxx>
> > ---
> >   include/linux/alloc_tag.h | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
> > index e867461585ff..afc9e259a2d3 100644
> > --- a/include/linux/alloc_tag.h
> > +++ b/include/linux/alloc_tag.h
> > @@ -12,6 +12,7 @@
> >   #include <asm/percpu.h>
> >   #include <linux/cpumask.h>
> >   #include <linux/static_key.h>
> > +#include <linux/irqflags.h>
>
> Actually, shouldn't this end up in a percpu header? Or was there a
> problem with that?

If I understand it correctly, linux/alloc_tag.h does not include 
linux/percpu.h (which has that include) to avoid a circular dependency 
as linux/percpu.h includes linux/alloc_tag.h. It instead includes 
arch-specific asm/percpu.h, and as a consequence it doesn't always get 
linux/irqflags.h.

It's also entirely possible that I've mixed something up, I really don't 
have much experience developing for the kernel.