Re: powerpc: build failures in Linus' tree

[Willy Tarreau <w@1wt.eu>]

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Hi again Stephen,

On Sun, Aug 02, 2020 at 07:20:19PM +0200, Willy Tarreau wrote:
> On Sun, Aug 02, 2020 at 08:48:42PM +1000, Stephen Rothwell wrote:
> > Hi all,
> > 
> > We are getting build failures in some PowerPC configs for Linus' tree.
> > See e.g. http://kisskb.ellerman.id.au/kisskb/buildresult/14306515/
> > 
> > In file included from /kisskb/src/arch/powerpc/include/asm/paca.h:18,
> >                  from /kisskb/src/arch/powerpc/include/asm/percpu.h:13,
> >                  from /kisskb/src/include/linux/random.h:14,
> >                  from /kisskb/src/include/linux/net.h:18,
> >                  from /kisskb/src/net/ipv6/ip6_fib.c:20:
> > /kisskb/src/arch/powerpc/include/asm/mmu.h:139:22: error: unknown type name 'next_tlbcam_idx'
> >   139 | DECLARE_PER_CPU(int, next_tlbcam_idx);
> > 
> > I assume this is caused by commit
> > 
> >   1c9df907da83 ("random: fix circular include dependency on arm64 after addition of percpu.h")
> > 
> > But I can't see how, sorry.
> 
> So there, asm/mmu.h includes asm/percpu.h, which includes asm/paca.h, which
> includes asm/mmu.h.
> 
> I suspect that we can remove asm/paca.h from asm/percpu.h as it *seems*
> to be only used by the #define __my_cpu_offset but I don't know if anything
> will break further, especially if this __my_cpu_offset is used anywhere
> without this paca definition.

I tried this and it fixed 5.8 for me with your config above. I'm appending
a patch that does just this. I didn't test other configs as I don't know
which ones to test though. If it fixes the problem for you, maybe it can
be picked by the PPC maintainers.

Willy

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From bcd64a7d0f3445c9a75d3b4dc4837d2ce61660c9 Mon Sep 17 00:00:00 2001
From: Willy Tarreau <w@1wt.eu>
Date: Mon, 3 Aug 2020 05:27:57 +0200
Subject: powerpc: fix circular dependency in percpu.h

After random.h started to include percpu.h (commit f227e3e), several
archs broke in circular dependencies around percpu.h.

In https://lore.kernel.org/lkml/20200802204842.36bca162@canb.auug.org.au/
Stephen Rothwell reported breakage for powerpc with CONFIG_PPC_FSL_BOOK3E.

It turns out that asm/percpu.h includes asm/paca.h, which itself
includes mmu.h, which includes percpu.h when CONFIG_PPC_FSL_BOOK3E=y.

Percpu seems to include asm/paca.h only for local_paca which is used in
the __my_cpu_offset macro. Removing this include solves the issue for
this config.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Fixes: f227e3e ("random32: update the net random state on interrupt and activity")
Link: https://lore.kernel.org/lkml/20200802204842.36bca162@canb.auug.org.au/
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
 arch/powerpc/include/asm/percpu.h | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/powerpc/include/asm/percpu.h b/arch/powerpc/include/asm/percpu.h
index dce863a..cd3f6e5 100644
--- a/arch/powerpc/include/asm/percpu.h
+++ b/arch/powerpc/include/asm/percpu.h
@@ -10,8 +10,6 @@
 
 #ifdef CONFIG_SMP
 
-#include <asm/paca.h>
-
 #define __my_cpu_offset local_paca->data_offset
 
 #endif /* CONFIG_SMP */
-- 
2.9.0