linux-kernel - Re: [PATCH 2/2] perf tests: add test for trace output loss

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Message-ID: <CAEmfU+v8KR3Bd8w7kOX6ScGig106zh5gW9P5fwAw-BF3tmAp7A@mail.gmail.com>
Date: Thu, 14 Nov 2024 09:44:56 -0800
From: Benjamin Peterson <benjamin@...flow.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	"Liang, Kan" <kan.liang@...ux.intel.com>, open list <linux-kernel@...r.kernel.org>, 
	"open list:PERFORMANCE EVENTS SUBSYSTEM" <linux-perf-users@...r.kernel.org>
Subject: Re: [PATCH 2/2] perf tests: add test for trace output loss

On Thu, Nov 14, 2024 at 9:43 AM Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
>
> On Thu, Nov 14, 2024 at 02:37:52PM -0300, Arnaldo Carvalho de Melo wrote:
> > On Wed, Nov 06, 2024 at 11:45:18PM +0000, Benjamin Peterson wrote:
> > > Add a test that checks that trace output is not lost to races. This is
> > > accomplished by tracing the exit_group syscall of "true" multiple times and
> > > checking for correct output.
> > >
> > > Conveniently, this test also serves as a regression test for 5fb8e56542a3 ("perf
> > > trace: avoid garbage when not printing a trace event's arguments") because
> > > exit_group triggers the previously buggy printing behavior.
> > >
> > > Signed-off-by: Benjamin Peterson <benjamin@...flow.com>
> > > ---
> > >  tools/perf/tests/shell/trace_exit_race.sh | 31 +++++++++++++++++++++++
> > >  1 file changed, 31 insertions(+)
> > >  create mode 100755 tools/perf/tests/shell/trace_exit_race.sh
> > >
> > > diff --git a/tools/perf/tests/shell/trace_exit_race.sh b/tools/perf/tests/shell/trace_exit_race.sh
> > > new file mode 100755
> > > index 000000000000..8b70324bc5b4
> > > --- /dev/null
> > > +++ b/tools/perf/tests/shell/trace_exit_race.sh
> > > @@ -0,0 +1,31 @@
> > > +#!/bin/sh
> > > +# perf trace exit race
> > > +# SPDX-License-Identifier: GPL-2.0
> > > +
> > > +# Check that the last events of a perf trace'd subprocess are not
> > > +# lost. Specifically, trace the exiting syscall of "true" 100 times and ensure
> > > +# the output contains 100 correct lines.
> > > +
> > > +# shellcheck source=lib/probe.sh
> > > +. "$(dirname $0)"/lib/probe.sh
> > > +
> > > +skip_if_no_perf_trace || exit 2
> > > +
> > > +trace_shutdown_race() {
> > > +   for i in $(seq 100); do
> > > +           perf trace -e syscalls:sys_enter_exit_group true 2>>$file
> > > +   done
> > > +   [ $(grep -c -E " +[0-9]+\.[0-9]+ +true/[0-9]+ syscalls:sys_enter_exit_group\(\)$" $file) = "100" ]
> > > +}
> > > +
> > > +
> > > +file=$(mktemp /tmp/temporary_file.XXXXX)
> > > +
> > > +# Do not use whatever ~/.perfconfig file, it may change the output
> > > +# via trace.{show_timestamp,show_prefix,etc}
> > > +export PERF_CONFIG=/dev/null
> > > +
> > > +trace_shutdown_race
> > > +err=$?
> > > +rm -f ${file}
> > > +exit $err
> > > --
> >
> > Its failing with shellcheck, I'm trying to fix it:
> >
> >   CC      /tmp/build/perf-tools-next/builtin-trace.o
> >   TEST    /tmp/build/perf-tools-next/tests/shell/trace_exit_race.sh.shellcheck_log
> >
> > In tests/shell/trace_exit_race.sh line 15:
> >       for i in $(seq 100); do
> >         ^-^ SC2034 (warning): i appears unused. Verify use (or export if used externally).
> >
> >
> > In tests/shell/trace_exit_race.sh line 18:
> >       [ $(grep -c -E " +[0-9]+\.[0-9]+ +true/[0-9]+ syscalls:sys_enter_exit_group\(\)$" $file) = "100" ]
> >           ^-- SC2046 (warning): Quote this to prevent word splitting.
> >
> > For more information:
> >   https://www.shellcheck.net/wiki/SC2034 -- i appears unused. Verify use (or ...
> >   https://www.shellcheck.net/wiki/SC2046 -- Quote this to prevent word splitt...
> > make[4]: *** [tests/Build:91: /tmp/build/perf-tools-next/tests/shell/trace_exit_race.sh.shellcheck_log] Error 1
> > make[3]: *** [/home/acme/git/perf-tools-next/tools/build/Makefile.build:158: tests] Error 2
> > make[2]: *** [Makefile.perf:777: /tmp/build/perf-tools-next/perf-test-in.o] Error 2
> > make[2]: *** Waiting for unfinished jobs....
>
> I've read the links provided by ShellCheck and folded this to satisfy
> it, please consider installing ShellCheck, the perf build process will
> use it when avaiable.

Thank you.

>
> - Arnaldo
>
> diff --git a/tools/perf/tests/shell/trace_exit_race.sh b/tools/perf/tests/shell/trace_exit_race.sh
> index 8b70324bc5b4fb4c..c37ed6bb9f7e8fab 100755
> --- a/tools/perf/tests/shell/trace_exit_race.sh
> +++ b/tools/perf/tests/shell/trace_exit_race.sh
> @@ -12,10 +12,10 @@
>  skip_if_no_perf_trace || exit 2
>
>  trace_shutdown_race() {
> -       for i in $(seq 100); do
> +       for _ in $(seq 100); do
>                 perf trace -e syscalls:sys_enter_exit_group true 2>>$file
>         done
> -       [ $(grep -c -E " +[0-9]+\.[0-9]+ +true/[0-9]+ syscalls:sys_enter_exit_group\(\)$" $file) = "100" ]
> +       [ "$(grep -c -E ' +[0-9]+\.[0-9]+ +true/[0-9]+ syscalls:sys_enter_exit_group\(\)$' $file)" = "100" ]
>  }

This all looks okay.