linux-kernel - Re: [PATCH 1/2] powerpc: drop dependency on <asm/machdep.h> in archrandom.h

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Message-ID: <Yt7Ewi2vu49fW1ZJ@yury-laptop>
Date:   Mon, 25 Jul 2022 09:28:50 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-kernel@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linuxppc-dev@...ts.ozlabs.org,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH 1/2] powerpc: drop dependency on <asm/machdep.h> in
 archrandom.h

On Mon, Jul 25, 2022 at 10:22:13PM +1000, Michael Ellerman wrote:
> Michael Ellerman <mpe@...erman.id.au> writes:
> > Yury Norov <yury.norov@...il.com> writes:
> >> archrandom.h includes <asm/machdep.h> to refer ppc_md. This causes
> >> circular header dependency, if generic nodemask.h  includes random.h:
> >>
> >> In file included from include/linux/cred.h:16,
> >>                  from include/linux/seq_file.h:13,
> >>                  from arch/powerpc/include/asm/machdep.h:6,
> >>                  from arch/powerpc/include/asm/archrandom.h:5,
> >>                  from include/linux/random.h:109,
> >>                  from include/linux/nodemask.h:97,
> >>                  from include/linux/list_lru.h:12,
> >>                  from include/linux/fs.h:13,
> >>                  from include/linux/compat.h:17,
> >>                  from arch/powerpc/kernel/asm-offsets.c:12:
> >> include/linux/sched.h:1203:9: error: unknown type name 'nodemask_t'
> >>  1203 |         nodemask_t                      mems_allowed;
> >>       |         ^~~~~~~~~~
> >>
> >> Fix it by removing <asm/machdep.h> dependency from archrandom.h
> >>
> >> Signed-off-by: Yury Norov <yury.norov@...il.com>
> >> ---
> >>  arch/powerpc/include/asm/archrandom.h |  9 +--------
> >>  arch/powerpc/kernel/setup-common.c    | 11 +++++++++++
> >>  2 files changed, 12 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h
> >> index 9a53e29680f4..21def59ef1a6 100644
> >> --- a/arch/powerpc/include/asm/archrandom.h
> >> +++ b/arch/powerpc/include/asm/archrandom.h
> >> @@ -4,7 +4,7 @@
> >>  
> >>  #ifdef CONFIG_ARCH_RANDOM
> >>  
> >> -#include <asm/machdep.h>
> >> +bool __must_check arch_get_random_seed_long(unsigned long *v);
> >>  
> >>  static inline bool __must_check arch_get_random_long(unsigned long *v)
> >>  {
> >> @@ -16,13 +16,6 @@ static inline bool __must_check arch_get_random_int(unsigned int *v)
> >>  	return false;
> >>  }
> >>  
> >> -static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
> >> -{
> >> -	if (ppc_md.get_random_seed)
> >> -		return ppc_md.get_random_seed(v);
> >> -
> >> -	return false;
> >> -}
> >
> > I'd rather we didn't have to force this out of line.
> >
> > I think I see a different way to fix it, I'll just do some more build
> > tests.
> 
> Of course my idea didn't work :}
> 
> So I'll just ack your patch for now, and maybe I can get the headers
> cleaned up in future to allow it to be out-of-line again.

I understand that it looks like a tradeoff - we inline a couple of small
functions with the cost of uninlining an almost innocent victim. 

The complete solution would be probably a splitting ppc_md declaration
out of asm/machdep.h. I wanted to do that, but I'm not a PPC guy, and
just don't know how to split the header correctly.

Anyways, thanks for the ack. Applied on bitmap-for-next.

Thanks,
Yury