[00/18] random: Include <linux/percpu.h> and resolve circular include dependency

There were several attempts to resolve circular include dependency
after the addition of percpu.h: 1c9df907da83 ("random: fix circular
include dependency on arm64 after addition of percpu.h"), c0842fbc1b18
("random32: move the pseudo-random 32-bit definitions to prandom.h") and
finally d9f29deb7fe8 ("prandom: Remove unused include") that completely
removes inclusion of <linux/percpu.h>.

Due to legacy reasons, <linux/random.h> includes <linux/prandom.h>, but
with the commit entry remark:

--quote--
A further cleanup step would be to remove this from <linux/random.h>
entirely, and make people who use the prandom infrastructure include
just the new header file.  That's a bit of a churn patch, but grepping
for "prandom_" and "next_pseudo_random32" "struct rnd_state" should
catch most users.

But it turns out that that nice cleanup step is fairly painful, because
a _lot_ of code currently seems to depend on the implicit include of
<linux/random.h>, which can currently come in a lot of ways, including
such fairly core headfers as <linux/net.h>.

So the "nice cleanup" part may or may never happen.
--/quote--

__percpu tag is currently defined in include/linux/compiler_types.h,
so there is no direct need for the inclusion of <linux/percpu.h>.
However, in [1] we would like to repurpose __percpu tag as a named
address space qualifier, where __percpu macro uses defines from
<linux/percpu.h>.

This patch series is the "nice cleanup" part, and allows us to finally
include <linux/percpu.h> in prandom.h.

The whole series was tested by compiling the kernel for x86_64 allconfig
and some popular architectures, namely arm64 defconfig, powerpc defconfig
and loongarch defconfig.

[1] https://lore.kernel.org/lkml/20240812115945.484051-4-ubizjak@gmail.com/

Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tursulin@ursulin.net>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: "Theodore Y. Ts'o" <tytso@mit.edu>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Hannes Reinecke <hare@suse.de>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: Song Liu <song@kernel.org>
Cc: Yonghong Song <yonghong.song@linux.dev>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Stanislav Fomichev <sdf@fomichev.me>
Cc: Hao Luo <haoluo@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: David Gow <davidgow@google.com>
Cc: Rae Moar <rmoar@google.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Uros Bizjak <ubizjak@gmail.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Cc: linux-media@vger.kernel.org
Cc: linux-mtd@lists.infradead.org
Cc: linux-fscrypt@vger.kernel.org
Cc: linux-scsi@vger.kernel.org
Cc: bpf@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Cc: kunit-dev@googlegroups.com

Uros Bizjak (18):
  x86/kaslr: Include <linux/prandom.h> instead of <linux/random.h>
  drm/i915/selftests: Include <linux/prandom.h> instead of
    <linux/random.h>
  drm/lib: Include <linux/prandom.h> instead of <linux/random.h>
  media: vivid: Include <linux/prandom.h> in vivid-vid-cap.c
  mtd: tests: Include <linux/prandom.h> instead of <linux/random.h>
  fscrypt: Include <linux/prandom.h> instead of <linux/random.h>
  scsi: libfcoe: Include <linux/prandom.h> instead of <linux/random.h>
  bpf: Include <linux/prandom.h> instead of <linux/random.h>
  lib/interval_tree_test.c: Include <linux/prandom.h> instead of
    <linux/random.h>
  kunit: string-stream-test: Include <linux/prandom.h> instead of
    <linux/random.h>
  random32: Include <linux/prandom.h> instead of <linux/random.h>
  lib/rbtree-test: Include <linux/prandom.h> instead of <linux/random.h>
  bpf/tests: Include <linux/prandom.h> instead of <linux/random.h>
  lib/test_parman: Include <linux/prandom.h> instead of <linux/random.h>
  lib/test_scanf: Include <linux/prandom.h> instead of <linux/random.h>
  netem: Include <linux/prandom.h> in sch_netem.c
  random: Do not include <linux/prandom.h>
  prandom: Include <linux/percpu.h>

 arch/x86/mm/kaslr.c                              | 2 +-
 drivers/gpu/drm/i915/selftests/i915_gem.c        | 2 +-
 drivers/gpu/drm/i915/selftests/i915_random.h     | 2 +-
 drivers/gpu/drm/i915/selftests/scatterlist.c     | 2 +-
 drivers/gpu/drm/lib/drm_random.h                 | 2 +-
 drivers/media/test-drivers/vivid/vivid-vid-cap.c | 1 +
 drivers/mtd/tests/oobtest.c                      | 2 +-
 drivers/mtd/tests/pagetest.c                     | 2 +-
 drivers/mtd/tests/subpagetest.c                  | 2 +-
 fs/crypto/keyring.c                              | 2 +-
 include/linux/prandom.h                          | 1 +
 include/linux/random.h                           | 7 -------
 include/scsi/libfcoe.h                           | 2 +-
 kernel/bpf/core.c                                | 2 +-
 lib/interval_tree_test.c                         | 2 +-
 lib/kunit/string-stream-test.c                   | 1 +
 lib/random32.c                                   | 2 +-
 lib/rbtree_test.c                                | 2 +-
 lib/test_bpf.c                                   | 2 +-
 lib/test_parman.c                                | 2 +-
 lib/test_scanf.c                                 | 2 +-
 net/sched/sch_netem.c                            | 1 +
 22 files changed, 21 insertions(+), 24 deletions(-)
  

On Thu, Sep 05, 2024 at 02:17:08PM +0200, Uros Bizjak wrote:
> There were several attempts to resolve circular include dependency
> after the addition of percpu.h: 1c9df907da83 ("random: fix circular
> include dependency on arm64 after addition of percpu.h"), c0842fbc1b18
> ("random32: move the pseudo-random 32-bit definitions to prandom.h") and
> finally d9f29deb7fe8 ("prandom: Remove unused include") that completely
> removes inclusion of <linux/percpu.h>.
> 
> Due to legacy reasons, <linux/random.h> includes <linux/prandom.h>, but
> with the commit entry remark:
> 
> --quote--
> A further cleanup step would be to remove this from <linux/random.h>
> entirely, and make people who use the prandom infrastructure include
> just the new header file.  That's a bit of a churn patch, but grepping
> for "prandom_" and "next_pseudo_random32" "struct rnd_state" should
> catch most users.
> 
> But it turns out that that nice cleanup step is fairly painful, because
> a _lot_ of code currently seems to depend on the implicit include of
> <linux/random.h>, which can currently come in a lot of ways, including
> such fairly core headfers as <linux/net.h>.
> 
> So the "nice cleanup" part may or may never happen.
> --/quote--
> 
> __percpu tag is currently defined in include/linux/compiler_types.h,
> so there is no direct need for the inclusion of <linux/percpu.h>.
> However, in [1] we would like to repurpose __percpu tag as a named
> address space qualifier, where __percpu macro uses defines from
> <linux/percpu.h>.
> 
> This patch series is the "nice cleanup" part, and allows us to finally
> include <linux/percpu.h> in prandom.h.
> 
> The whole series was tested by compiling the kernel for x86_64 allconfig
> and some popular architectures, namely arm64 defconfig, powerpc defconfig
> and loongarch defconfig.

Obvious question(s) is(are):
1) have you seen the Ingo's gigantic patch series towards resolving issues with
the headers?
2) if not, please look at the preliminary work and take something from there, I
believe there are many useful changes already waiting for a couple of years to
be applied.

Because I haven't found any references nor mentions of that in the cover letter
here and explanation why it was not taking into consideration.

> [1] https://lore.kernel.org/lkml/20240812115945.484051-4-ubizjak@gmail.com/
  

On Thu, Sep 5, 2024 at 2:41 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Thu, Sep 05, 2024 at 02:17:08PM +0200, Uros Bizjak wrote:
> > There were several attempts to resolve circular include dependency
> > after the addition of percpu.h: 1c9df907da83 ("random: fix circular
> > include dependency on arm64 after addition of percpu.h"), c0842fbc1b18
> > ("random32: move the pseudo-random 32-bit definitions to prandom.h") and
> > finally d9f29deb7fe8 ("prandom: Remove unused include") that completely
> > removes inclusion of <linux/percpu.h>.
> >
> > Due to legacy reasons, <linux/random.h> includes <linux/prandom.h>, but
> > with the commit entry remark:
> >
> > --quote--
> > A further cleanup step would be to remove this from <linux/random.h>
> > entirely, and make people who use the prandom infrastructure include
> > just the new header file.  That's a bit of a churn patch, but grepping
> > for "prandom_" and "next_pseudo_random32" "struct rnd_state" should
> > catch most users.
> >
> > But it turns out that that nice cleanup step is fairly painful, because
> > a _lot_ of code currently seems to depend on the implicit include of
> > <linux/random.h>, which can currently come in a lot of ways, including
> > such fairly core headfers as <linux/net.h>.
> >
> > So the "nice cleanup" part may or may never happen.
> > --/quote--
> >
> > __percpu tag is currently defined in include/linux/compiler_types.h,
> > so there is no direct need for the inclusion of <linux/percpu.h>.
> > However, in [1] we would like to repurpose __percpu tag as a named
> > address space qualifier, where __percpu macro uses defines from
> > <linux/percpu.h>.
> >
> > This patch series is the "nice cleanup" part, and allows us to finally
> > include <linux/percpu.h> in prandom.h.
> >
> > The whole series was tested by compiling the kernel for x86_64 allconfig
> > and some popular architectures, namely arm64 defconfig, powerpc defconfig
> > and loongarch defconfig.
>
> Obvious question(s) is(are):
> 1) have you seen the Ingo's gigantic patch series towards resolving issues with
> the headers?
> 2) if not, please look at the preliminary work and take something from there, I
> believe there are many useful changes already waiting for a couple of years to
> be applied.
>
> Because I haven't found any references nor mentions of that in the cover letter
> here and explanation why it was not taking into consideration.

I am aware of the series, but the patch takes only a small bite of it
and specifically resolves the inclusion of <linux/prandom.h> from
linux/random.h. The series fixes the missing inclusion of
<linux/prandom.h> in files that use pseudo-random function and it was
not meant to be a general header cleanup. The end goal is to allow us
to include <linux/percpu.h> in linux/prandom.h - which uses __percpu
tag without the correct include.

Thus, the patch series is only tangentially connected to Ingo's patch series.

Best regards,
Uros.
  

On Thu, Sep 05, 2024 at 03:03:24PM +0200, Uros Bizjak wrote:
> On Thu, Sep 5, 2024 at 2:41 PM Andy Shevchenko
> <andriy.shevchenko@linux.intel.com> wrote:
> >
> > On Thu, Sep 05, 2024 at 02:17:08PM +0200, Uros Bizjak wrote:
> > > There were several attempts to resolve circular include dependency
> > > after the addition of percpu.h: 1c9df907da83 ("random: fix circular
> > > include dependency on arm64 after addition of percpu.h"), c0842fbc1b18
> > > ("random32: move the pseudo-random 32-bit definitions to prandom.h") and
> > > finally d9f29deb7fe8 ("prandom: Remove unused include") that completely
> > > removes inclusion of <linux/percpu.h>.
> > >
> > > Due to legacy reasons, <linux/random.h> includes <linux/prandom.h>, but
> > > with the commit entry remark:
> > >
> > > --quote--
> > > A further cleanup step would be to remove this from <linux/random.h>
> > > entirely, and make people who use the prandom infrastructure include
> > > just the new header file.  That's a bit of a churn patch, but grepping
> > > for "prandom_" and "next_pseudo_random32" "struct rnd_state" should
> > > catch most users.
> > >
> > > But it turns out that that nice cleanup step is fairly painful, because
> > > a _lot_ of code currently seems to depend on the implicit include of
> > > <linux/random.h>, which can currently come in a lot of ways, including
> > > such fairly core headfers as <linux/net.h>.
> > >
> > > So the "nice cleanup" part may or may never happen.
> > > --/quote--
> > >
> > > __percpu tag is currently defined in include/linux/compiler_types.h,
> > > so there is no direct need for the inclusion of <linux/percpu.h>.
> > > However, in [1] we would like to repurpose __percpu tag as a named
> > > address space qualifier, where __percpu macro uses defines from
> > > <linux/percpu.h>.
> > >
> > > This patch series is the "nice cleanup" part, and allows us to finally
> > > include <linux/percpu.h> in prandom.h.
> > >
> > > The whole series was tested by compiling the kernel for x86_64 allconfig
> > > and some popular architectures, namely arm64 defconfig, powerpc defconfig
> > > and loongarch defconfig.
> >
> > Obvious question(s) is(are):
> > 1) have you seen the Ingo's gigantic patch series towards resolving issues with
> > the headers?
> > 2) if not, please look at the preliminary work and take something from there, I
> > believe there are many useful changes already waiting for a couple of years to
> > be applied.
> >
> > Because I haven't found any references nor mentions of that in the cover letter
> > here and explanation why it was not taking into consideration.
> 
> I am aware of the series, but the patch takes only a small bite of it
> and specifically resolves the inclusion of <linux/prandom.h> from
> linux/random.h. The series fixes the missing inclusion of
> <linux/prandom.h> in files that use pseudo-random function and it was
> not meant to be a general header cleanup. The end goal is to allow us
> to include <linux/percpu.h> in linux/prandom.h - which uses __percpu
> tag without the correct include.

Thank you for elaboration, it's all clear now.

> Thus, the patch series is only tangentially connected to Ingo's patch series.