linux-kernel - Re: [PATCH 03/10] x86: arch/x86/Kconfig.cpu unification

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Date:	Tue, 06 Nov 2007 02:10:27 -0500
From:	Brian Gerst <bgerst@...ntduck.org>
To:	Adrian Bunk <bunk@...nel.org>
CC:	Sam Ravnborg <sam@...nborg.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/10] x86: arch/x86/Kconfig.cpu unification

Adrian Bunk wrote:
> On Tue, Nov 06, 2007 at 03:46:30AM +0100, Sam Ravnborg wrote:
>> On Mon, Nov 05, 2007 at 07:53:39PM -0500, Brian Gerst wrote:
>>> Sam Ravnborg wrote:
>>>> Move all CPU definitions to Kconfig.cpu
>>> This patch causes build failure on x86_64:
>>>
>>> lib/rwsem.c: In function ‘__init_rwsem’:
>>> lib/rwsem.c:24: error: ‘struct rw_semaphore’ has no member named ‘count’
>>> lib/rwsem.c:24: error: ‘RWSEM_UNLOCKED_VALUE’ undeclared (first use in
>>> this function)
>>> lib/rwsem.c:24: error: (Each undeclared identifier is reported only once
>>> lib/rwsem.c:24: error: for each function it appears in.)
>>> lib/rwsem.c: In function ‘__rwsem_do_wake’:
>>> lib/rwsem.c:64: error: implicit declaration of function
>>> ‘rwsem_atomic_update’
>>> lib/rwsem.c:64: error: ‘RWSEM_ACTIVE_BIAS’ undeclared (first use in this
>>> function)
>>> lib/rwsem.c:66: error: ‘RWSEM_ACTIVE_MASK’ undeclared (first use in this
>>> function)
>>> lib/rwsem.c:115: error: ‘RWSEM_WAITING_BIAS’ undeclared (first use in
>>> this function)
>>> lib/rwsem.c:120: error: implicit declaration of function ‘rwsem_atomic_add’
>>> lib/rwsem.c: In function ‘rwsem_down_failed_common’:
>>> lib/rwsem.c:169: error: ‘RWSEM_ACTIVE_MASK’ undeclared (first use in
>>> this function)
>>> lib/rwsem.c: In function ‘rwsem_down_read_failed’:
>>> lib/rwsem.c:197: error: ‘RWSEM_WAITING_BIAS’ undeclared (first use in
>>> this function)
>>> lib/rwsem.c:197: error: ‘RWSEM_ACTIVE_BIAS’ undeclared (first use in
>>> this function)
>>> lib/rwsem.c: In function ‘rwsem_down_write_failed’:
>>> lib/rwsem.c:210: error: ‘RWSEM_ACTIVE_BIAS’ undeclared (first use in
>>> this function)
>>>
>>> git bisect gives:
>>> 55432d383871d127685d78f94e0ad60307dcc0e9 is first bad commit
>>> commit 55432d383871d127685d78f94e0ad60307dcc0e9
>>> Author: Sam Ravnborg <sam@...nborg.org>
>>> Date:   Thu Nov 1 21:54:39 2007 +0100
>>>
>>>     x86: arch/x86/Kconfig.cpu unification
>> Seems that a default value fail to change value when we shift
>> from 32 to 64 bit. I have it reproduced here.
>> Will look at it tonight.
> 
> The problem is that you source arch/x86/Kconfig.cpu from 
> arch/x86/Kconfig.x86_64 but didn't give RWSEM_XCHGADD_ALGORITHM 
> the required dependency on X86_32.
> 
>> 	Sam
> 
> cu
> Adrian
> 

The quick fix is to move the RWSEM_XCHGADD_ALGORITHM and
RWSEM_XCHGADD_ALGORITHM defines from Kconfig.cpu to Kconfig.i386.

Looking at this closer, the 64-bit code has been using the generic
spinlock-based implementation, while the 32-bit code uses an optimized
version on all but true 386 cpus.  The 64-bit code should be adapted to
use the optimized version at some point.
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