Re: [PATCH v2 1/5] perf: arm64: Add test to check userspace access to hardware counters.

[Raphael Gault]

Hi Arnaldo,

On 7/5/19 3:54 PM, Arnaldo Carvalho de Melo wrote:
> Em Fri, Jul 05, 2019 at 09:55:37AM +0100, Raphael Gault escreveu:
> > This test relies on the fact that the PMU registers are accessible
> > from userspace. It then uses the perf_event_mmap_page to retrieve
> > the counter index and access the underlying register.
> >
> > This test uses sched_setaffinity(2) in order to run on all CPU and thus
> > check the behaviour of the PMU of all cpus in a big.LITTLE environment.
> >
> > Signed-off-by: Raphael Gault <raphael.gault@xxxxxxx>
> > ---
> >   tools/perf/arch/arm64/include/arch-tests.h |   6 +
> >   tools/perf/arch/arm64/tests/Build          |   1 +
> >   tools/perf/arch/arm64/tests/arch-tests.c   |   4 +
> >   tools/perf/arch/arm64/tests/user-events.c  | 255 +++++++++++++++++++++
> >   4 files changed, 266 insertions(+)
> >   create mode 100644 tools/perf/arch/arm64/tests/user-events.c
> >
> > diff --git a/tools/perf/arch/arm64/include/arch-tests.h b/tools/perf/arch/arm64/include/arch-tests.h
> > index 90ec4c8cb880..a9b17ae0560b 100644
> > --- a/tools/perf/arch/arm64/include/arch-tests.h
> > +++ b/tools/perf/arch/arm64/include/arch-tests.h
> > @@ -2,11 +2,17 @@
> >   #ifndef ARCH_TESTS_H
> >   #define ARCH_TESTS_H
> >   
> > +#define __maybe_unused	__attribute__((unused))
>
>
> What is wrong with using:
>
> #include <linux/compiler.h>
>
> ?
>
> [acme@quaco perf]$ find tools/perf/ -name "*.[ch]" | xargs grep __maybe_unused | wc -l
> 1115
> [acme@quaco perf]$ grep __maybe_unused tools/include/linux/compiler.h
> #ifndef __maybe_unused
> # define __maybe_unused		__attribute__((unused))
> [acme@quaco perf]$
>
> Also please don't break strings in multiple lines just to comply with
> the 80 column limit. That is ok when you have multiple lines ending with
> a newline, but otherwise just makes it look ugly.

You're right, I shall correct those points.

Thanks,

--
Raphael Gault