linux-kernel - Re: [PATCH] Define smp_call_function

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Message-ID: <471F5CAB.9020300@qumranet.com>
Date:	Wed, 24 Oct 2007 16:54:35 +0200
From:	Avi Kivity <avi@...ranet.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	kvm-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	jeff@...zik.org, bunk@...nel.org
Subject: Re: [PATCH] Define smp_call_function_mask() on uniprocessor builds

Andrew Morton wrote:
> On Wed, 24 Oct 2007 10:51:25 +0200 Avi Kivity <avi@...ranet.com> wrote:
>
>   
>> Rather than #ifdef users of smp_call_function_mask(), define it as an
>> empty macro to avoid build errors.  The function explicitly prohibits
>> callers from specifying the current cpu, so nothing needs to be done.
>>
>> This unbreaks uniprocessor KVM builds.
>>
>> Signed-off-by: Avi Kivity <avi@...ranet.com>
>>
>> diff --git a/include/linux/smp.h b/include/linux/smp.h
>> index 259a13c..24e2e31 100644
>> --- a/include/linux/smp.h
>> +++ b/include/linux/smp.h
>> @@ -108,6 +108,9 @@ static inline void smp_send_reschedule(int cpu) { }
>>  	0;			\
>>  })
>>  
>> +#define smp_call_function_mask(mask, func, info, wait) \
>> +	do { (void)(mask); (void)(func); (void)(info); (void)(wait); } while (0)
>> +
>>  #endif /* !SMP */
>>  
>>  /*
>>     
>
> The real smp_call_function_mask() returns int, so this version should do so
> also.
>
>   

Right.  Ingo sent a patch which does this.

[I can't think of a way to use that int though]

> An inlined C function will provide the needed references to the arguments -
> no need for those funny (void) thingies.  And it will provide typechecking.
>   

Last time I did this (on smp_call_function_single()), the build broke on 
a zillion-and-a-half archs due to include file hell.  That got patched 
into a macro. I saw the cpumask_t in there and got cold feet.

-- 
error compiling committee.c: too many arguments to function

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