The build looks for "python" and "python-config", while modern
distributions provide only "python3" and "python3-config" by default.
Suggest installing "python-is-python3" and "python-dev-is-python3", as
available on Debian 11 (bullseye) and Ubuntu 20.04 LTS (focal) and
later.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 tools/perf/Makefile.config | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index a6448a804ee53a36..b37149afdb1d27ba 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -872,7 +872,7 @@ ifdef NO_LIBPYTHON
 else
 
   ifndef PYTHON
-    $(call disable-python,No python interpreter was found: disables Python support - please install python-devel/python-dev)
+    $(call disable-python,No python interpreter was found: disables Python support - please install python-devel/python-dev/python-dev-is-python3)
   else
     PYTHON_WORD := $(call shell-wordify,$(PYTHON))
 
@@ -915,7 +915,7 @@ endif
 ifneq ($(NO_JEVENTS),1)
   NO_JEVENTS := 0
   ifndef PYTHON
-    $(error ERROR: No python interpreter found for jevents generation. Install python or build with NO_JEVENTS=1.)
+    $(error ERROR: No python interpreter found for jevents generation. Install python/python-is-python3 or build with NO_JEVENTS=1.)
   else
     # jevents.py uses f-strings present in Python 3.6 released in Dec. 2016.
     JEVENTS_PYTHON_GOOD := $(shell $(PYTHON) -c 'import sys;print("1" if(sys.version_info.major >= 3 and sys.version_info.minor >= 6) else "0")' 2> /dev/null)
-- 
2.43.0

Hi Geert,

On Thu, Oct 16, 2025 at 02:44:12PM +0200, Geert Uytterhoeven wrote:
> The build looks for "python" and "python-config", while modern
> distributions provide only "python3" and "python3-config" by default.
> Suggest installing "python-is-python3" and "python-dev-is-python3", as
> available on Debian 11 (bullseye) and Ubuntu 20.04 LTS (focal) and
> later.

Seems to me, this change is not necessary. The Makefile [1] searches
python[2|3]/python[2|3]-cofig if un-versioned executables are not found.

I confirmed that I can build successfully without installation
python-dev-is-python3 package.

Thanks,
Leo

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/perf/Makefile.config?//h=v6.18-rc1#n302

Hi Leo,

On Fri, 17 Oct 2025 at 14:29, Leo Yan <leo.yan@arm.com> wrote:
> On Thu, Oct 16, 2025 at 02:44:12PM +0200, Geert Uytterhoeven wrote:
> > The build looks for "python" and "python-config", while modern
> > distributions provide only "python3" and "python3-config" by default.
> > Suggest installing "python-is-python3" and "python-dev-is-python3", as
> > available on Debian 11 (bullseye) and Ubuntu 20.04 LTS (focal) and
> > later.
>
> Seems to me, this change is not necessary. The Makefile [1] searches
> python[2|3]/python[2|3]-cofig if un-versioned executables are not found.
>
> I confirmed that I can build successfully without installation
> python-dev-is-python3 package.

    $ sudo apt remove python-dev-is-python3 python-is-python3
    $ make tools/perf

Indeed, it still works. I am quite sure I had to install both, and
even verified that uninstalling them again broke the build again before
creating my patch.

/me dives deeper.

Aha, I found it.  After uninstalling python3-dev, I got into the same
state as yesterday:

    $ make tools/perf
    [...]
    Makefile.config:875: No python interpreter was found: disables
Python support - please install python-devel/python-dev
    Makefile.config:918: *** ERROR: No python interpreter needed for
jevents generation. Install python or build with NO_JEVENTS=1..  Stop.

So these error messages sound like python is missing. And "python"
is indeed missing, but "python3" is available.
Hence I installed python-is-python3, but that turned out not to be
sufficient.
Hence I also installed python-dev-is-python3, and that fixed the issue,
as python-dev-is-python3 depends on python3-dev, so the latter was
installed, too.

After removing python-is-python3 and python-dev-is-python3, everything
keeps on working.  But if you never installed python3-dev manually,
and run "sudo apt autoremove", python3-dev is uninstalled, reintroducing
the issue.

So just recomming to install python-dev-is-python3 in the error
message should be sufficient?

What do you think?
Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Hello,

On Fri, Oct 17, 2025 at 06:39:04PM +0200, Geert Uytterhoeven wrote:
> Hi Leo,
> 
> On Fri, 17 Oct 2025 at 14:29, Leo Yan <leo.yan@arm.com> wrote:
> > On Thu, Oct 16, 2025 at 02:44:12PM +0200, Geert Uytterhoeven wrote:
> > > The build looks for "python" and "python-config", while modern
> > > distributions provide only "python3" and "python3-config" by default.
> > > Suggest installing "python-is-python3" and "python-dev-is-python3", as
> > > available on Debian 11 (bullseye) and Ubuntu 20.04 LTS (focal) and
> > > later.
> >
> > Seems to me, this change is not necessary. The Makefile [1] searches
> > python[2|3]/python[2|3]-cofig if un-versioned executables are not found.
> >
> > I confirmed that I can build successfully without installation
> > python-dev-is-python3 package.
> 
>     $ sudo apt remove python-dev-is-python3 python-is-python3
>     $ make tools/perf
> 
> Indeed, it still works. I am quite sure I had to install both, and
> even verified that uninstalling them again broke the build again before
> creating my patch.
> 
> /me dives deeper.
> 
> Aha, I found it.  After uninstalling python3-dev, I got into the same
> state as yesterday:
> 
>     $ make tools/perf
>     [...]
>     Makefile.config:875: No python interpreter was found: disables
> Python support - please install python-devel/python-dev
>     Makefile.config:918: *** ERROR: No python interpreter needed for
> jevents generation. Install python or build with NO_JEVENTS=1..  Stop.
> 
> So these error messages sound like python is missing. And "python"
> is indeed missing, but "python3" is available.
> Hence I installed python-is-python3, but that turned out not to be
> sufficient.
> Hence I also installed python-dev-is-python3, and that fixed the issue,
> as python-dev-is-python3 depends on python3-dev, so the latter was
> installed, too.
> 
> After removing python-is-python3 and python-dev-is-python3, everything
> keeps on working.  But if you never installed python3-dev manually,
> and run "sudo apt autoremove", python3-dev is uninstalled, reintroducing
> the issue.
> 
> So just recomming to install python-dev-is-python3 in the error
> message should be sufficient?
> 
> What do you think?
> Thanks!

Thanks for looking at the issue.

I think the code was to deal with either python2 or python3 in the past
and we removed python2 support recently.  I don't know if any distro
made 'python' to refer python3 and removed 'python3' otherwise we can
just check python3.

Thanks,
Namhyung

On Sun, Oct 19, 2025 at 11:49:56AM +0900, Namhyung Kim wrote:

[...]

> > Aha, I found it.  After uninstalling python3-dev, I got into the same
> > state as yesterday:
> > 
> >     $ make tools/perf
> >     [...]
> >     Makefile.config:875: No python interpreter was found: disables
> > Python support - please install python-devel/python-dev
> >     Makefile.config:918: *** ERROR: No python interpreter needed for
> > jevents generation. Install python or build with NO_JEVENTS=1..  Stop.
> > 
> > So these error messages sound like python is missing. And "python"
> > is indeed missing, but "python3" is available.
> > Hence I installed python-is-python3, but that turned out not to be
> > sufficient.
> > Hence I also installed python-dev-is-python3, and that fixed the issue,
> > as python-dev-is-python3 depends on python3-dev, so the latter was
> > installed, too.
> > 
> > After removing python-is-python3 and python-dev-is-python3, everything
> > keeps on working.  But if you never installed python3-dev manually,
> > and run "sudo apt autoremove", python3-dev is uninstalled, reintroducing
> > the issue.
> > 
> > So just recomming to install python-dev-is-python3 in the error
> > message should be sufficient?
> > 
> > What do you think?

Can we explicitly suggest that developers install python3-devel or
python3-dev instead?  Two reasons:

- python-dev-is-python3 is specific to Ubuntu/Debian; some distros do
  not provide this package and even advocate against using unversioned
  "/usr/bin/python" shebangs [1].

- As Namhyung mentioned, perf has removed Python 2 support (at least
  this is claimed), it is straightforward to install only the Python3
  packages.

[...]

> I think the code was to deal with either python2 or python3 in the past
> and we removed python2 support recently.  I don't know if any distro
> made 'python' to refer python3 and removed 'python3' otherwise we can
> just check python3.

I agreed with only checking python3 - neat and compatible for distros.

Just note, some legacy python shebangs are left, we can update to
"#!/usr/bin/env python3" but this can be done separately.

  $ git grep "#\!.*/usr/bin.*python"
  python/tracepoint.py:#! /usr/bin/env python
  python/twatch.py:#! /usr/bin/env python
  scripts/python/export-to-postgresql.py:#   #!/usr/bin/python2
  scripts/python/exported-sql-viewer.py:#!/usr/bin/env python
  scripts/python/libxed.py:#!/usr/bin/env python
  tests/shell/lib/perf_json_output_lint.py:#!/usr/bin/python

Thanks,
Leo

[1] https://fedoraproject.org/wiki/Changes/Move_usr_bin_python_into_separate_package#Motivation

Hi Leo,

On Mon, 20 Oct 2025 at 11:31, Leo Yan <leo.yan@arm.com> wrote:
> On Sun, Oct 19, 2025 at 11:49:56AM +0900, Namhyung Kim wrote:
> > > Aha, I found it.  After uninstalling python3-dev, I got into the same
> > > state as yesterday:
> > >
> > >     $ make tools/perf
> > >     [...]
> > >     Makefile.config:875: No python interpreter was found: disables
> > > Python support - please install python-devel/python-dev
> > >     Makefile.config:918: *** ERROR: No python interpreter needed for
> > > jevents generation. Install python or build with NO_JEVENTS=1..  Stop.
> > >
> > > So these error messages sound like python is missing. And "python"
> > > is indeed missing, but "python3" is available.
> > > Hence I installed python-is-python3, but that turned out not to be
> > > sufficient.
> > > Hence I also installed python-dev-is-python3, and that fixed the issue,
> > > as python-dev-is-python3 depends on python3-dev, so the latter was
> > > installed, too.
> > >
> > > After removing python-is-python3 and python-dev-is-python3, everything
> > > keeps on working.  But if you never installed python3-dev manually,
> > > and run "sudo apt autoremove", python3-dev is uninstalled, reintroducing
> > > the issue.
> > >
> > > So just recomming to install python-dev-is-python3 in the error
> > > message should be sufficient?
> > >
> > > What do you think?
>
> Can we explicitly suggest that developers install python3-devel or
> python3-dev instead?  Two reasons:
>
> - python-dev-is-python3 is specific to Ubuntu/Debian; some distros do
>   not provide this package and even advocate against using unversioned
>   "/usr/bin/python" shebangs [1].
>
> - As Namhyung mentioned, perf has removed Python 2 support (at least
>   this is claimed), it is straightforward to install only the Python3
>   packages.

Suggesting python3-dev sounds good to me.
None of the two checks:

    ifndef PYTHON
      $(call disable-python,No python interpreter was found: disables
Python support - please install python-devel/python-dev)

    ifndef PYTHON
      $(error ERROR: No python interpreter found for jevents
generation. Install python or build with NO_JEVENTS=1.)

seem to be about the python interpreter anyway, but about the python
development environment.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Hi Geert,

On Mon, Oct 20, 2025 at 12:15:22PM +0200, Geert Uytterhoeven wrote:

[...]

> > Can we explicitly suggest that developers install python3-devel or
> > python3-dev instead?  Two reasons:
> >
> > - python-dev-is-python3 is specific to Ubuntu/Debian; some distros do
> >   not provide this package and even advocate against using unversioned
> >   "/usr/bin/python" shebangs [1].
> >
> > - As Namhyung mentioned, perf has removed Python 2 support (at least
> >   this is claimed), it is straightforward to install only the Python3
> >   packages.
> 
> Suggesting python3-dev sounds good to me.

It is good to mention both python3-devel / python3-dev (one is for Fedora
and another is for Debian/Ubuntu).  Sorry for confusion.

> None of the two checks:
> 
>     ifndef PYTHON
>       $(call disable-python,No python interpreter was found: disables
> Python support - please install python-devel/python-dev)
> 
>     ifndef PYTHON
>       $(error ERROR: No python interpreter found for jevents
> generation. Install python or build with NO_JEVENTS=1.)
> 
> seem to be about the python interpreter anyway, but about the python
> development environment.

Either is fine for me.

Thanks,
Leo

> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> -- 
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds