Re: [2.6.37-rc1] /proc/vmstat failure.

[Wu Fengguang <fengguang.wu@intel.com>]

On Thu, Nov 04, 2010 at 10:52:51AM +0800, Américo Wang wrote:
> On Thu, Nov 04, 2010 at 10:20:52AM +0800, Wu Fengguang wrote:
> >On Thu, Nov 04, 2010 at 05:54:48AM +0800, Tetsuo Handa wrote:
> >> Wu Fengguang wrote:
> >> > On Wed, Nov 03, 2010 at 07:11:11PM +0800, Tetsuo Handa wrote:
> >> > > Hello.
> >> > > 
> >> > > "cat /proc/vmstat" triggered below failure.
> >> > > 
> >> > > BUG: unable to handle kernel paging request at 07c06d16
> >> > > IP: [<c050c336>] strnlen+0x6/0x20
> >> > 
> >> > It seems that m->private is of type (void *) while the original v is
> >> > (unsigned long *). Can be fixed by the following patch.
> >> 
> >> Fixed by this patch. Thank you.
> >
> >Great, thanks!
> >
> >> By the way, GCC treats "(void *) + offset" as "(char *) + offset"
> >> but it is GCC specific extention. Maybe we should avoid such usage
> >> in order to avoid build failure for other compilers.
> >
> >"(void *) + offset" seems to be used quite often.
> >
> >I tried enable this gcc option, only to see huge amount of warnings.
> >
> >       -Wpointer-arith
> >           Warn about anything that depends on the "size of" a
> >           function type or of "void".  GNU C assigns these types a
> >           size of 1, for convenience in calculations with "void *"
> >           pointers and pointers to functions.
> >
> 
> Yup! I think it is good to have this.
> 
> >/cc/linux-next/scripts/mod/file2alias.c:88: warning: pointer of type ‘void *’ used in arithmetic
> ...
> >/cc/linux-next/scripts/mod/modpost.c:1565: warning: pointer of type ‘void *’ used in arithmetic
> >
> 
> No problem, this is from kbuild and most of them that I checked are actually fine,
> we can send patches to remove these warnings.

Confirmed. Now my full kernel build is complete and the above are the
only warnings I see. So it should be easy to add the -Wpointer-arith
check.

Thanks,
Fengguang