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

From: Raphael Gault
Date: Mon Jul 08 2019 - 03:10:51 EST

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
[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.


Raphael Gault