linux-kernel - Re: cannot build Linux 4.4: arch/mips/kernel/signal.c:142:12: error: ‘struct ucontext’ has no member named ‘uc

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Date:	Mon, 18 Jan 2016 18:22:21 -0800
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Heinrich Schuchardt <xypron.glpk@....de>,
	lkml <linux-kernel@...r.kernel.org>, linux-mips@...ux-mips.org
Cc:	Ralf Baechle <ralf@...ux-mips.org>,
	Paul Burton <paul.burton@...tec.com>,
	James Hogan <james.hogan@...tec.com>,
	linux-kbuild@...r.kernel.org, Michal Marek <mmarek@...e.com>
Subject: Re: cannot build Linux 4.4: arch/mips/kernel/signal.c:142:12: error: ‘struct ucontext’ has no member named ‘uc_extcontext’

Le 17/01/2016 06:48, Heinrich Schuchardt a écrit :
> On 01/17/2016 02:54 PM, Heinrich Schuchardt wrote:
>>
>> HEAD is now at afd2ff9... Linux 4.4
>> arch/mips/kernel/signal.c: In function ‘sc_to_extcontext’:
>> arch/mips/kernel/signal.c:142:12: error: ‘struct ucontext’ has no member
>> named ‘uc_extcontext’
>>   return &uc->uc_extcontext;
>>             ^
>> In file included from include/linux/poll.h:11:0,
>>                  from include/linux/ring_buffer.h:7,
>>                  from include/linux/trace_events.h:5,
>>                  from include/trace/syscall.h:6,
>>                  from include/linux/syscalls.h:81,
>>                  from arch/mips/kernel/signal.c:26:
>> arch/mips/kernel/signal.c: In function ‘save_msa_extcontext’:
>> arch/mips/kernel/signal.c:170:40: error: dereferencing pointer to
>> incomplete type
>>
> 
> The problem stemmed from make not recognizing that this file was outdated:
> 
> Oct 16  2014 arch/mips/include/generated/asm/ucontext.h
> 
> Shouldn't make automatically regenerate outdated files?

The reduced test case can be simplified to these steps:

git co f1fe2d21f4e1aca8644cea888dc618f0183ad671\^1
configure your kernel
ARCH=mips make arch/mips/kernel/signal.o
git co f1fe2d21f4e1aca8644cea888dc618f0183ad671
ARCH=mips make arch/mips/kernel/signal.o

The problem seems to be that if there was a previous build which
resulted in creating an asm-generic wrapper for a file
(arch/mips/include/generated/asm/ucontext.h in that case), but this file
was later moved into an arch-specific, non asm-generic header file, then
we are just not going to automatically remove this auto-generated
wrapper, and generate the new one.

This seems to be aggravated by the fact that commit
f1fe2d21f4e1aca8644cea888dc618f0183ad671 does not add ucontext.h to
arch/mips/include/uapi/Kbuild, Paul, James is that intentional?

After trying to mess a bit with a clean solution, I just gave up and
decided that this was not worth fixing since it is a very infrequent
problem.
-- 
Florian