linux-kernel - Re: [PATCH v2 1/2] perf test workload noploop: Name the noploop process

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Message-ID: <CAP-5=fVGPKOVc7WA=VygSE3BKN90tSpLPhkaupX_fUboBcyHPg@mail.gmail.com>
Date: Mon, 23 Jun 2025 12:41:09 -0700
From: Ian Rogers <irogers@...gle.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>, Sebastian Andrzej Siewior <bigeasy@...utronix.de>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, 
	linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2 1/2] perf test workload noploop: Name the noploop process

On Mon, Jun 23, 2025 at 12:19 PM Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
>
> On Mon, Jun 23, 2025 at 11:14:47AM -0700, Namhyung Kim wrote:
> > On Mon, Jun 23, 2025 at 11:05:41AM -0700, Ian Rogers wrote:
> > > On Mon, Jun 23, 2025 at 10:45 AM Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
> > > > On Mon, Jun 23, 2025 at 08:12:47AM -0700, Ian Rogers wrote:
> > > > > On Fri, Jun 20, 2025 at 12:36 PM Namhyung Kim <namhyung@...nel.org> wrote:
> > > > > > I'm afraid it'd introduce a build failure on musl.  Please see
>
> > > > > > https://lore.kernel.org/linux-perf-users/20250611092542.F4ooE2FL@linutronix.de/
>
> > > > > > I think <sys/prctl.h> would be enough.
>
> > > > > we could do that but in the glibc man page it says:
> > > > > https://man7.org/linux/man-pages/man2/prctl.2.html
> > > > > ```
> > > > > #include <linux/prctl.h>  /* Definition of PR_* constants */
> > > > > #include <sys/prctl.h>
> > > > > ```
>
> > > > > It'd be nice to think musl was slowly getting fixed. I notice we're
>
> > > > Sebastian reported on the musl libc, its maintainer replied:
>
> > > > https://www.openwall.com/lists/musl/2025/06/12/11
>
> > > Ugh. I'm not sure how we're expected to resolve this and have glibc
> > > and musl be happy without basically not trusting libc.
>
> > Maybe pthread_setname_np()?  It seems musl also implemented it.
>
> ⬢ [acme@...lbx perf-tools-next]$ git diff
> diff --git a/tools/perf/tests/workloads/noploop.c b/tools/perf/tests/workloads/noploop.c
> index 8b954d4660833a2f..656e472e618822a3 100644
> --- a/tools/perf/tests/workloads/noploop.c
> +++ b/tools/perf/tests/workloads/noploop.c
> @@ -1,9 +1,8 @@
>  /* SPDX-License-Identifier: GPL-2.0 */
> +#include <pthread.h>
>  #include <stdlib.h>
>  #include <signal.h>
>  #include <unistd.h>
> -#include <linux/prctl.h>
> -#include <sys/prctl.h>
>  #include <linux/compiler.h>
>  #include "../tests.h"
>
> @@ -18,7 +17,7 @@ static int noploop(int argc, const char **argv)
>  {
>         int sec = 1;
>
> -       prctl(PR_SET_NAME, "perf-noploop");
> +       pthread_setname_np(pthread_self(), "perf-noploop");
>         if (argc > 0)
>                 sec = atoi(argv[0]);
>
> ⬢ [acme@...lbx perf-tools-next]$
>
> ⬢ [acme@...lbx perf-tools-next]$ perf test -w noploop &
> [1] 1179763
> ⬢ [acme@...lbx perf-tools-next]$ ps
>     PID TTY          TIME CMD
>    3935 pts/1    00:00:00 bash
>    4053 pts/1    00:00:00 toolbox
>    4222 pts/1    00:00:28 podman
>  971900 pts/1    00:00:00 bash
> 1100453 pts/1    00:00:00 tail
> 1160346 pts/1    00:00:00 bash
> 1179763 pts/1    00:00:00 perf-noploop
> 1179765 pts/1    00:00:00 ps
> ⬢ [acme@...lbx perf-tools-next]$
>
> And then on one of the Alpine Linux containers:
>
> make: Leaving directory '/tmp/perf-6.16.0-rc3/tools/perf'
> /tmp/perf-6.16.0-rc3 $ cat /etc/os-release
> NAME="Alpine Linux"
> ID=alpine
> VERSION_ID=3.18.12
> PRETTY_NAME="Alpine Linux v3.18"
> HOME_URL="https://alpinelinux.org/"
> BUG_REPORT_URL="https://gitlab.alpinelinux.org/alpine/aports/-/issues"
> /tmp/perf-6.16.0-rc3 $ tools/perf/perf test -w noploop &
> /tmp/perf-6.16.0-rc3 $ ps
> PID   USER     TIME  COMMAND
>     1 toolsbui  0:00 /bin/sh
>  5693 toolsbui  0:00 {perf-noploop} tools/perf/perf test -w noploop
>  5694 toolsbui  0:00 ps
> /tmp/perf-6.16.0-rc3 $
> [1]+  Done                       tools/perf/perf test -w noploop
> /tmp/perf-6.16.0-rc3
>
> There are more direct use of prctl() to set the name in tools/perf/,
> using pthread_setname_np() seems cleaner :-)

Yeah, I wanted to set the program name rather than a thread name for
the sake of seeing the process name in ps - hence reaching for prctl.
PR_SET_NAME is documented as setting the thread name and so no
difference to pthread_setname_np. It's still frustrating to get bogged
down in working around musl when typing the literal code from the
prctl man page. Do you need me to re-send the patch?

Thanks,
Ian

> - Arnaldo