Re: [PATCH] kfifo: remove unnecessary type check

[Yuanhan Liu]

On Fri, Oct 26, 2012 at 05:52:44PM +0800, Richard Yang wrote:
> On Fri, Oct 26, 2012 at 02:11:45PM +0800, Yuanhan Liu wrote:
> >On Fri, Oct 26, 2012 at 07:38:31AM +0200, Stefani Seibold wrote:
> >> Am Freitag, den 26.10.2012, 09:46 +0800 schrieb Yuanhan Liu:
> >> > From: Yuanhan Liu <yuanhan.liu@xxxxxxxxxxxxxxx>
> >> > 
> >> > Firstly, this kind of type check doesn't work. It does something similay
> >> > like following:
> >> > 	void * __dummy = NULL;
> >> > 	__buf = __dummy;
> >> > 
> >> > __dummy is defined as void *. Thus it will not trigger warnings as
> >> > expected.
> >> > 
> >> > Second, we don't need that kind of check. Since the prototype
> >> > of __kfifo_out is:
> >> > 	unsigned int __kfifo_out(struct __kfifo *fifo,  void *buf, unsigned int len)
> >> > 
> >> > buf is defined as void *, so we don't need do the type check. Remove it.
> >> > 
> >> > LINK: https://lkml.org/lkml/2012/10/25/386
> >> > LINK: https://lkml.org/lkml/2012/10/25/584
> >> > 
> >> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> >> > Cc: Wei Yang <weiyang@xxxxxxxxxxxxxxxxxx>
> >> > Cc: Stefani Seibold <stefani@xxxxxxxxxxx>
> >> > Cc: Fengguang Wu <fengguang.wu@xxxxxxxxx>
> >> > Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> >> > Signed-off-by: Yuanhan Liu <yuanhan.liu@xxxxxxxxxxxxxxx>
> >> > ---
> >> >  include/linux/kfifo.h | 20 --------------------
> >> >  1 file changed, 20 deletions(-)
> >> > 
> >> > diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h
> >> > index 10308c6..b8c1d03 100644
> >> > --- a/include/linux/kfifo.h
> >> > +++ b/include/linux/kfifo.h
> >> > @@ -390,10 +390,6 @@ __kfifo_int_must_check_helper( \
> >> >  	unsigned int __ret; \
> >> >  	const size_t __recsize = sizeof(*__tmp->rectype); \
> >> >  	struct __kfifo *__kfifo = &__tmp->kfifo; \
> >> > -	if (0) { \
> >> > -		typeof(__tmp->ptr_const) __dummy __attribute__ ((unused)); \
> >> > -		__dummy = (typeof(__val))NULL; \
> >> > -	} \
> >> >  	if (__recsize) \
> >> >  		__ret = __kfifo_in_r(__kfifo, __val, sizeof(*__val), \
> >> >  			__recsize); \
> >> > @@ -432,8 +428,6 @@ __kfifo_uint_must_check_helper( \
> >> >  	unsigned int __ret; \
> >> >  	const size_t __recsize = sizeof(*__tmp->rectype); \
> >> >  	struct __kfifo *__kfifo = &__tmp->kfifo; \
> >> > -	if (0) \
> >> > -		__val = (typeof(__tmp->ptr))0; \
> >> >  	if (__recsize) \
> >> >  		__ret = __kfifo_out_r(__kfifo, __val, sizeof(*__val), \
> >> >  			__recsize); \
> >> > @@ -473,8 +467,6 @@ __kfifo_uint_must_check_helper( \
> >> >  	unsigned int __ret; \
> >> >  	const size_t __recsize = sizeof(*__tmp->rectype); \
> >> >  	struct __kfifo *__kfifo = &__tmp->kfifo; \
> >> > -	if (0) \
> >> > -		__val = (typeof(__tmp->ptr))NULL; \
> >> >  	if (__recsize) \
> >> >  		__ret = __kfifo_out_peek_r(__kfifo, __val, sizeof(*__val), \
> >> >  			__recsize); \
> >> > @@ -512,10 +504,6 @@ __kfifo_uint_must_check_helper( \
> >> >  	unsigned long __n = (n); \
> >> >  	const size_t __recsize = sizeof(*__tmp->rectype); \
> >> >  	struct __kfifo *__kfifo = &__tmp->kfifo; \
> >> > -	if (0) { \
> >> > -		typeof(__tmp->ptr_const) __dummy __attribute__ ((unused)); \
> >> > -		__dummy = (typeof(__buf))NULL; \
> >> > -	} \
> >> >  	(__recsize) ?\
> >> >  	__kfifo_in_r(__kfifo, __buf, __n, __recsize) : \
> >> >  	__kfifo_in(__kfifo, __buf, __n); \
> >> > @@ -565,10 +553,6 @@ __kfifo_uint_must_check_helper( \
> >> >  	unsigned long __n = (n); \
> >> >  	const size_t __recsize = sizeof(*__tmp->rectype); \
> >> >  	struct __kfifo *__kfifo = &__tmp->kfifo; \
> >> > -	if (0) { \
> >> > -		typeof(__tmp->ptr) __dummy = NULL; \
> >> > -		__buf = __dummy; \
> >> > -	} \
> >> >  	(__recsize) ?\
> >> >  	__kfifo_out_r(__kfifo, __buf, __n, __recsize) : \
> >> >  	__kfifo_out(__kfifo, __buf, __n); \
> >> > @@ -777,10 +761,6 @@ __kfifo_uint_must_check_helper( \
> >> >  	unsigned long __n = (n); \
> >> >  	const size_t __recsize = sizeof(*__tmp->rectype); \
> >> >  	struct __kfifo *__kfifo = &__tmp->kfifo; \
> >> > -	if (0) { \
> >> > -		typeof(__tmp->ptr) __dummy __attribute__ ((unused)) = NULL; \
> >> > -		__buf = __dummy; \
> >> > -	} \
> >> >  	(__recsize) ? \
> >> >  	__kfifo_out_peek_r(__kfifo, __buf, __n, __recsize) : \
> >> >  	__kfifo_out_peek(__kfifo, __buf, __n); \
> >> 
> >> Did you tried to compile the whole kernel including all the drivers with
> >> your patch?
> >
> >Hi Stefani,
> >
> >I did a build test, it did't introduce any new compile errors and
> >warnings. While, I haven't tried make allmodconfig then. Does this patch
> >seems wrong to you?
> 
> Hmm, in my mind, those warnings are produced by the code you removed.
> So it is reasonable that you see no new warnings.

Hi Yang,

Nope. It's not hard to tell they are old warnings. And as you can see from
the email I posted, I did a build compile with and without applying this
patch, and does make C=2 2>/tmp/out.{before,after}. I then compared the
two file, they are exactly same. So, no new warnings introduced.

Thanks,
Yuanhan Liu
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