linux-kernel - Re: [PATCH] check spinlock_t/rwlock_t argument type on non-SMP builds

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Date:	Fri, 03 Jul 2009 20:02:01 +0100
From:	Dave <kilroyd@...glemail.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	David Kilroy <kilroyd@...glemail.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] check spinlock_t/rwlock_t argument type on non-SMP builds

Ingo Molnar wrote:
> * David Kilroy <kilroyd@...glemail.com> wrote:
> 
>> When writing code for UP without CONFIG_DEBUG_SPINLOCK it's easy 
>> to get the first argument to the spinlock/rwlock functions wrong. 
>> This is because the parameter is not actually used in this 
>> configuration.
>>
>> Typically you will only find out it's wrong
>>  * by rebuilding with CONFIG_SMP or CONFIG_DEBUG_SPINLOCK
>>  * after you've submitted your beautiful patch series.
>>
>> The first means a long wait, and the latter is a bit late.
>>
>> Add typechecking on the first argument of these macro functions. 
>> Note that since the typecheck now references the variable, the 
>> explicit read is redundant and can be removed.
>>
>> This change causes compiler warnings in net/ipv4/route.c, as this 
>> passes NULL as the first argument in the UP configuration. Simply 
>> cast this.
> 
> Wondering - can the wrappers be moved from CPP land to C land by 
> turning them into inlines? (i havent checked all usages so there 
> might be some surprises, but by and large it ought to be possible.)

I thought about doing it that way. I decided not to because I suspected
it would be harder to verify that the behaviour is unchanged.

Also the _lock_irqsave functions output to the flags parameter (which
isn't a pointer) so that has to remain a macro.

If you'd really rather an inline version, I can spend some time looking
into it.


Dave.
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