>-----Original Message----- >From: Satyam Sharma [mailto:[EMAIL PROTECTED] >Sent: Wednesday, May 09, 2007 11:30 AM >To: Pallipadi, Venkatesh >Cc: Jarek Poplawski; Andrew Morton; >linux-kernel@vger.kernel.org; Oleg Nesterov >Subject: Re: [PATCH -mm] timer: parenthesis fix in >tbase_get_deferrable() etc. > >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; linux-kernel@vger.kernel.org; >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: >> >> >> >> > >> >> > Signed-off-by: Jarek Poplawski <[EMAIL PROTECTED]> >> >> > >> >> > --- >> >> > >> >> > diff -Nurp 2.6.21-mm1-/kernel/timer.c 2.6.21-mm1/kernel/timer.c >> >> > --- 2.6.21-mm1-/kernel/timer.c 2007-05-08 >> >11:54:48.000000000 +0200 >> >> > +++ 2.6.21-mm1/kernel/timer.c 2007-05-08 >> >12:05:11.000000000 +0200 >> >> > @@ -92,24 +92,24 @@ static DEFINE_PER_CPU(tvec_base_t *, tve >> >> > /* Functions below help us manage 'deferrable' flag */ >> >> > 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? >> >> 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.
On a 64 bit system, converting pointer to int causes unnecessary compiler warning, and intermediate long conversion was to avoid that. I will have to rephrase my comment to remove 32 bit value and use int, as that is what the function returns. Thanks, Venki - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
