linux-kernel - Re: [PATCH v4 48/48] perf cpumap: Give CPUs their own type.

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Date:   Sun, 9 Jan 2022 21:45:19 -0800
From:   Ian Rogers <irogers@...gle.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        John Garry <john.garry@...wei.com>,
        Kajol Jain <kjain@...ux.ibm.com>,
        "Paul A . Clarke" <pc@...ibm.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Riccardo Mancini <rickyman7@...il.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Vineet Singh <vineet.singh@...el.com>,
        James Clark <james.clark@....com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, zhengjun.xing@...el.com,
        eranian@...gle.com
Subject: Re: [PATCH v4 48/48] perf cpumap: Give CPUs their own type.

On Sun, Jan 9, 2022 at 10:30 AM Jiri Olsa <jolsa@...hat.com> wrote:
>
> On Tue, Jan 04, 2022 at 10:13:51PM -0800, Ian Rogers wrote:
> > A common problem is confusing CPU map indices with the CPU, by wrapping
> > the CPU with a struct then this is avoided. This approach is similar to
> > atomic_t.
> >
> > Suggested-by: John Garry <john.garry@...wei.com>
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
>
> SNIP
>
> >  tools/perf/util/stat.h                        |   2 +-
> >  tools/perf/util/svghelper.c                   |   6 +-
> >  tools/perf/util/synthetic-events.c            |  12 +-
> >  tools/perf/util/synthetic-events.h            |   3 +-
> >  tools/perf/util/util.h                        |   5 +-
> >  59 files changed, 408 insertions(+), 347 deletions(-)
>
> that's massive ;-) did it find any mis-use of the index/value?

It did. The fixes precede this patch so that we can have the fixes
without the large rename.

> how about the same for threads?

Agreed, but the patch set was already big enough.

> > diff --git a/tools/lib/perf/include/internal/cpumap.h b/tools/lib/perf/include/internal/cpumap.h
> > index 71a31ed738c9..581f9ffb4237 100644
> > --- a/tools/lib/perf/include/internal/cpumap.h
> > +++ b/tools/lib/perf/include/internal/cpumap.h
> > @@ -4,6 +4,11 @@
> >
> >  #include <linux/refcount.h>
> >
> > +/** A wrapper around a CPU to avoid confusion with the perf_cpu_map's map's indices. */
> > +struct perf_cpu {
> > +     int cpu;
> > +};
>
> should we use 'int val' or 'int v' instead, so we don't have cpu.cpu ?

I can rename it if you have a preference.

Thanks,
Ian

> jirka
>
> SNIP
>