On Mon, 21 Jan 2008 02:22:23 -0800 (PST)
David Miller <[EMAIL PROTECTED]> wrote:
> From: Patrick McHardy <[EMAIL PROTECTED]>
> Date: Mon, 21 Jan 2008 01:16:32 +0100
>
> > Stephen Hemminger wrote:
> > > Replace loop in dsmark_valid_indices with equivalent bit math.
> > >
> > > Signed-off-by: Stephen Hemminger <[EMAIL PROTECTED]>
> > >
> > > --- a/net/sched/sch_dsmark.c 2008-01-20 13:07:58.000000000 -0800
> > > +++ b/net/sched/sch_dsmark.c 2008-01-20 13:22:54.000000000 -0800
> > > @@ -45,13 +45,8 @@ struct dsmark_qdisc_data {
> > >
> > > static inline int dsmark_valid_indices(u16 indices)
> > > {
> > > - while (indices != 1) {
> > > - if (indices & 1)
> > > - return 0;
> > > - indices >>= 1;
> > > - }
> > > -
> > > - return 1;
> > > + /* Must have only one bit set */
> > > + return (indices & (indices - 1)) == 0;
> >
> > hweight seems easier to understand, it took me a bit
> > to realize that the comment matches the code :)
>
> Sounds good. Here is what I ended up checking in.
>
> [PKT_SCHED] dsmark: Use hweight32() instead of convoluted loop.
>
> Based upon a patch by Stephen Hemminger and suggestions
> from Patrick McHardy.
>
> Signed-off-by: David S. Miller <[EMAIL PROTECTED]>
>
> diff --git a/net/sched/sch_dsmark.c b/net/sched/sch_dsmark.c
> index a9732ae..d96eaf0 100644
> --- a/net/sched/sch_dsmark.c
> +++ b/net/sched/sch_dsmark.c
> @@ -10,6 +10,7 @@
> #include <linux/errno.h>
> #include <linux/skbuff.h>
> #include <linux/rtnetlink.h>
> +#include <linux/bitops.h>
> #include <net/pkt_sched.h>
> #include <net/dsfield.h>
> #include <net/inet_ecn.h>
> @@ -43,17 +44,6 @@ struct dsmark_qdisc_data {
> int set_tc_index;
> };
>
> -static inline int dsmark_valid_indices(u16 indices)
> -{
> - while (indices != 1) {
> - if (indices & 1)
> - return 0;
> - indices >>= 1;
> - }
> -
> - return 1;
> -}
> -
> static inline int dsmark_valid_index(struct dsmark_qdisc_data *p, u16 index)
> {
> return (index <= p->indices && index > 0);
> @@ -348,7 +338,8 @@ static int dsmark_init(struct Qdisc *sch, struct rtattr
> *opt)
> goto errout;
>
> indices = RTA_GET_U16(tb[TCA_DSMARK_INDICES-1]);
> - if (!indices || !dsmark_valid_indices(indices))
> +
> + if (hweight32(indices) != 1)
> goto errout;
Come on Dave, that is a step backwards.
So you took a two instruction thing that any programmer who ever had one of
those
technical trick interviews would surely understand, and made it call a
function...
Seems like the thing you would consul others against.
Please use !is_power_of_2(indices) instead.
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