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

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Message-ID: <aFmooVYz-6p1DTSv@x1>
Date: Mon, 23 Jun 2025 16:18:57 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Ian Rogers <irogers@...gle.com>,
	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 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 :-)

- Arnaldo