On Wed, May 09, 2007 at 11:59:39PM +0530, Satyam Sharma wrote:
> On 5/9/07, Pallipadi, Venkatesh <[email protected]> wrote:
> >
> >>-----Original Message-----
> >>From: Jarek Poplawski [mailto:[email protected]]
> >>Sent: Tuesday, May 08, 2007 10:32 PM
> >>To: Andrew Morton
> >>Cc: Pallipadi, Venkatesh; [email protected]; Oleg Nesterov
> >>Subject: Re: [PATCH -mm] timer: parenthesis fix in
> >>tbase_get_deferrable() etc.
> >>
> >>On Tue, May 08, 2007 at 04:33:58PM -0700, Andrew Morton wrote:
> >>> On Tue, 8 May 2007 12:33:48 +0200
> >>> Jarek Poplawski <[email protected]> wrote:
...
> >>> > static inline unsigned int tbase_get_deferrable(tvec_base_t *base)
> >>> > {
> >>> > - return ((unsigned int)(unsigned long)base &
> >>TBASE_DEFERRABLE_FLAG);
> >>> > + return (unsigned int)((unsigned long)base &
> >>TBASE_DEFERRABLE_FLAG);
> >>> > }
> >>...
> >>> The change makes sense, but does it actually "fix" anything?
> >>>
> >>
> >>Yes - this first place fixes logical error, so it's a sin
> >>- even if not punishable in practice. (It's also unnecessary
> >>test for long to int conversion.)
> >>
> >
> >I am sorry, I don't understand. What is the logical error in the first
> >one?
I am sorry, too - for my "logic". It seems it's all correct!
(Except, I don't know what's going here...)
> >
> >Actually, your change makes it different from what was originally
> >indended.
> >Original intention was to type convert base to a 32 bit value and
> >bitwise& with FLAG.
>
> But that is not what the original code is doing. If you wanted to
> typecast "base" to "a 32 bit value" then you should've used u32
> instead.
>
> Anyway, if you originally intended to actually typecast "base" to
> unsigned int, then you could do that directly without typecasting it
> first to unsigned long (unnecessarily) and then to unsigned int. Of
> course, if your system implements a pointer as something bigger than
> unsigned int (which is what you eventually convert "base" to), then
> you're screwed anyway and the intermediate typecast to unsigned long
> doesn't buy you anything at all.
>
> The other 3 changes in this patch were clearly meaningless, though.
>
((unsigned int)(unsigned long)base ...
((tvec_base_t *)((unsigned long)base ...
((tvec_base_t *)((unsigned long)(timer->base) ...
(tvec_base_t *)((unsigned long)(new_base) ...
Yes, if you don't count reading this one close each other, they are
clearly meaningles.
Regards,
Jarek P.
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