linux-kernel - Re: [PATCH v4 6/8] sched: Replace strncmp with str_has

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Date:   Sat, 10 Aug 2019 01:04:35 +0800
From:   Chuhong Yuan <hslester96@...il.com>
To:     Valentin Schneider <valentin.schneider@....com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 6/8] sched: Replace strncmp with str_has_prefix

On Fri, Aug 9, 2019 at 7:31 PM Valentin Schneider
<valentin.schneider@....com> wrote:
>
> On 09/08/2019 08:10, Chuhong Yuan wrote:
> > strncmp(str, const, len) is error-prone because len
> > is easy to have typo.
> > The example is the hard-coded len has counting error
> > or sizeof(const) forgets - 1.
> > So we prefer using newly introduced str_has_prefix()
> > to substitute such strncmp to make code better.
> >
> > Signed-off-by: Chuhong Yuan <hslester96@...il.com>
>
> I tried to have a look at the series as a whole but it's not properly
> threaded (or at least doesn't appear as such on lore), which makes it
> unnecessarily annoying to review.
>
> Please make sure to use git-send-email, which should properly thread all
> patches (IOW make them in-reply-to the cover letter).
>

I have used git-send-email to send the series with a cover letter.
The cover letter is here:
https://lkml.org/lkml/2019/8/9/108

Indeed I find the series are not in the same thread, I am not sure
what is wrong with them.

>
> Other than that, I stared at it and it seems fine. It's not that helpful
> here since I doubt any of these prefixes will change in the near feature,
> but hey, why not.
>
> Reviewed-by: Valentin Schneider <valentin.schneider@....com>
>
> > ---
> > Changes in v4:
> >   - Eliminate assignments in if conditions.
> >
> >  kernel/sched/debug.c     |  6 ++++--
> >  kernel/sched/isolation.c | 11 +++++++----
> >  2 files changed, 11 insertions(+), 6 deletions(-)
> >
> > diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> > index f7e4579e746c..a03900523e5d 100644
> > --- a/kernel/sched/debug.c
> > +++ b/kernel/sched/debug.c
> > @@ -102,10 +102,12 @@ static int sched_feat_set(char *cmp)
> >  {
> >       int i;
> >       int neg = 0;
> > +     size_t len;
> >
> > -     if (strncmp(cmp, "NO_", 3) == 0) {
> > +     len = str_has_prefix(cmp, "NO_");
> > +     if (len) {
> >               neg = 1;
> > -             cmp += 3;
> > +             cmp += len;
> >       }
> >
> >       i = match_string(sched_feat_names, __SCHED_FEAT_NR, cmp);
> > diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
> > index ccb28085b114..ea2ead4b1906 100644
> > --- a/kernel/sched/isolation.c
> > +++ b/kernel/sched/isolation.c
> > @@ -141,16 +141,19 @@ __setup("nohz_full=", housekeeping_nohz_full_setup);
> >  static int __init housekeeping_isolcpus_setup(char *str)
> >  {
> >       unsigned int flags = 0;
> > +     size_t len;
> >
> >       while (isalpha(*str)) {
> > -             if (!strncmp(str, "nohz,", 5)) {
> > -                     str += 5;
> > +             len = str_has_prefix(str, "nohz,");
> > +             if (len) {
> > +                     str += len;
> >                       flags |= HK_FLAG_TICK;
> >                       continue;
> >               }
> >
> > -             if (!strncmp(str, "domain,", 7)) {
> > -                     str += 7;
> > +             len = str_has_prefix(str, "domain,");
> > +             if (len) {
> > +                     str += len;
> >                       flags |= HK_FLAG_DOMAIN;
> >                       continue;
> >               }
> >