powerpc: build failures in Linus' tree

powerpc: build failures in Linus' tree

[Stephen Rothwell]

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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.

-- 
Cheers,
Stephen Rothwell

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Re: powerpc: build failures in Linus' tree

[Willy Tarreau]

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.

Willy

Re: powerpc: build failures in Linus' tree

[Willy Tarreau]

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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

Re: powerpc: build failures in Linus' tree

[Stephen Rothwell]

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Hi Willy,

On Mon, 3 Aug 2020 05:45:47 +0200 Willy Tarreau <w@1wt.eu> wrote:
>
> 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:
> > > 
> > > 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.

Our mails have crossed.  I just sent a more comprehensive patch.  I
think your patch would require a lot of build testing and even then may
fail for some CONFIG combination that we didn't test or added in the
future (or someone just made up).

-- 
Cheers,
Stephen Rothwell

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Re: powerpc: build failures in Linus' tree

[Willy Tarreau]

On Mon, Aug 03, 2020 at 02:10:17PM +1000, Stephen Rothwell wrote:
> Our mails have crossed.

Ah indeed :-)

> I just sent a more comprehensive patch.  I
> think your patch would require a lot of build testing and even then may
> fail for some CONFIG combination that we didn't test or added in the
> future (or someone just made up).

Your looks far more complete and very likely more future-proof, I
totally agree.

Thanks!
Willy

Re: powerpc: build failures in Linus' tree

[Michael Ellerman]

Willy Tarreau <w@1wt.eu> writes:
> 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
> 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 */

If we just move the include of asm/paca.h below asm-generic/percpu.h
then it avoids the bad circular dependency and we still have paca.h
included from percpu.h as before.

eg:

diff --git a/arch/powerpc/include/asm/percpu.h b/arch/powerpc/include/asm/percpu.h
index dce863a7635c..8e5b7d0b851c 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 */
@@ -19,4 +17,6 @@
 
 #include <asm-generic/percpu.h>
 
+#include <asm/paca.h>
+
 #endif /* _ASM_POWERPC_PERCPU_H_ */


So I think I'm inclined to merge that as a minimal fix that's easy to
backport.

cheers

Re: powerpc: build failures in Linus' tree

[Willy Tarreau]

On Mon, Aug 03, 2020 at 09:18:00PM +1000, Michael Ellerman wrote:
> If we just move the include of asm/paca.h below asm-generic/percpu.h
> then it avoids the bad circular dependency and we still have paca.h
> included from percpu.h as before.
> 
> eg:
> 
> diff --git a/arch/powerpc/include/asm/percpu.h b/arch/powerpc/include/asm/percpu.h
> index dce863a7635c..8e5b7d0b851c 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 */
> @@ -19,4 +17,6 @@
>  
>  #include <asm-generic/percpu.h>
>  
> +#include <asm/paca.h>
> +
>  #endif /* _ASM_POWERPC_PERCPU_H_ */
> 
> 
> So I think I'm inclined to merge that as a minimal fix that's easy to
> backport.

This totally makes sense indeed!
Willy

Re: powerpc: build failures in Linus' tree

[Stephen Rothwell]

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Hi Michael,

On Mon, 03 Aug 2020 21:18:00 +1000 Michael Ellerman <mpe@ellerman.id.au> wrote:
>
> If we just move the include of asm/paca.h below asm-generic/percpu.h
> then it avoids the bad circular dependency and we still have paca.h
> included from percpu.h as before.
> 
> eg:
> 
> diff --git a/arch/powerpc/include/asm/percpu.h b/arch/powerpc/include/asm/percpu.h
> index dce863a7635c..8e5b7d0b851c 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 */
> @@ -19,4 +17,6 @@
>  
>  #include <asm-generic/percpu.h>
>  
> +#include <asm/paca.h>
> +
>  #endif /* _ASM_POWERPC_PERCPU_H_ */
> 
> 
> So I think I'm inclined to merge that as a minimal fix that's easy to
> backport.
> 
> cheers

Looks ok, except does it matter that the include used to be only done
if __powerpc64__ and CONFIG_SMP are defined?

-- 
Cheers,
Stephen Rothwell

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Re: powerpc: build failures in Linus' tree

[Michael Ellerman]

Stephen Rothwell <sfr@canb.auug.org.au> writes:
> On Mon, 03 Aug 2020 21:18:00 +1000 Michael Ellerman <mpe@ellerman.id.au> wrote:
>>
>> If we just move the include of asm/paca.h below asm-generic/percpu.h
>> then it avoids the bad circular dependency and we still have paca.h
>> included from percpu.h as before.
>> 
>> eg:
>> 
>> diff --git a/arch/powerpc/include/asm/percpu.h b/arch/powerpc/include/asm/percpu.h
>> index dce863a7635c..8e5b7d0b851c 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 */
>> @@ -19,4 +17,6 @@
>>  
>>  #include <asm-generic/percpu.h>
>>  
>> +#include <asm/paca.h>
>> +
>>  #endif /* _ASM_POWERPC_PERCPU_H_ */
>> 
>> 
>> So I think I'm inclined to merge that as a minimal fix that's easy to
>> backport.
>> 
>> cheers
>
> Looks ok, except does it matter that the include used to be only done
> if __powerpc64__ and CONFIG_SMP are defined?

Basically all of paca.h is inside #ifdef CONFIG_PPC64.

SMP "shouldn't matter", but I tested a SMP=n build and it's clean, so I
think it's good. Of course there's really no guarantees with these
header tangles.

cheers