linux-kernel - Re: [PATCH] mm/memprofiling: explicitly include irqflags.h in alloc

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Date: Sun, 7 Apr 2024 13:18:55 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Klara Modin <klarasmodin@...il.com>
Cc: akpm@...ux-foundation.org, surenb@...gle.com, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/memprofiling: explicitly include irqflags.h in
 alloc_tag.h

On Sun, Apr 07, 2024 at 07:12:04PM +0200, Klara Modin wrote:
> 
> 
> 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@gmail.com/
> > > Signed-off-by: Klara Modin <klarasmodin@...il.com>
> > > ---
> > >   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.

Gotcha

Acked-by: Kent Overstreet <kent.overstreet@...ux.dev>