[v5,0/7] Introduce __xchg, non-atomic xchg

  Hi all,

The helper is tiny and there are advices we can live without it, so
I want to present few arguments why it would be good to have it:

1. Code readability/simplification/number of lines:
  - decreases number of lines,
  - it often eliminates local variables,
  - for real examples see patches 3+.

2. Presence of similar helpers in other somehow related languages/libs:

a) Rust[1]: 'replace' from std::mem module, there is also 'take'
    helper (__xchg(&x, 0)), which is the same as private helper in
    i915 - fetch_and_zero, see latest patch.
b) C++ [2]: 'exchange' from utility header.

If the idea is OK there are still 2 questions to answer:

1. Name of the helper, __xchg follows kernel conventions,
    but for me Rust names are also OK.
2. Where to put the helper:
a) as in this patchset include/linux/non-atomic/xchg.h,
    proposed by Andy Shevchenko,
b) include/linux/utils.h ? any better name? Some kind
    of container for simple helpers.

All __xchg conversions were performed using cocci script,
then manually adjusted if necessary.

There is lot of places it can be used in, I have just chosen
some of them. I can provide cocci script to detect others (not all),
if necessary.

Changes:
v2: squashed all __xchg -> __arch_xchg t one patch (Arnd)
v3: fixed alpha/xchg_local (lkp@intel.com)
v4: adjusted indentation (Heiko)
v5: added more __xchg conversions - patches 3-6, added tags

[1]: https://doc.rust-lang.org/std/mem/index.html
[2]: https://en.cppreference.com/w/cpp/header/utility

Regards
Andrzej

Andrzej Hajda (7):
  arch: rename all internal names __xchg to __arch_xchg
  linux/include: add non-atomic version of xchg
  arch/*/uprobes: simplify arch_uretprobe_hijack_return_addr
  llist: simplify __llist_del_all
  io_uring: use __xchg if possible
  qed: use __xchg if possible
  drm/i915/gt: use __xchg instead of internal helper

 arch/alpha/include/asm/cmpxchg.h              | 10 +++++-----
 arch/arc/include/asm/cmpxchg.h                |  4 ++--
 arch/arm/include/asm/cmpxchg.h                |  7 ++++---
 arch/arm/probes/uprobes/core.c                |  8 ++------
 arch/arm64/include/asm/cmpxchg.h              |  7 +++----
 arch/arm64/kernel/probes/uprobes.c            |  9 ++-------
 arch/csky/kernel/probes/uprobes.c             |  9 ++-------
 arch/hexagon/include/asm/cmpxchg.h            | 10 +++++-----
 arch/ia64/include/asm/cmpxchg.h               |  2 +-
 arch/ia64/include/uapi/asm/cmpxchg.h          |  4 ++--
 arch/loongarch/include/asm/cmpxchg.h          |  4 ++--
 arch/m68k/include/asm/cmpxchg.h               |  6 +++---
 arch/mips/include/asm/cmpxchg.h               |  4 ++--
 arch/mips/kernel/uprobes.c                    | 10 ++--------
 arch/openrisc/include/asm/cmpxchg.h           | 10 +++++-----
 arch/parisc/include/asm/cmpxchg.h             |  4 ++--
 arch/powerpc/include/asm/cmpxchg.h            |  4 ++--
 arch/powerpc/kernel/uprobes.c                 | 10 ++--------
 arch/riscv/include/asm/atomic.h               |  2 +-
 arch/riscv/include/asm/cmpxchg.h              |  4 ++--
 arch/riscv/kernel/probes/uprobes.c            |  9 ++-------
 arch/s390/include/asm/cmpxchg.h               |  8 ++++----
 arch/s390/kernel/uprobes.c                    |  7 ++-----
 arch/sh/include/asm/cmpxchg.h                 |  4 ++--
 arch/sparc/include/asm/cmpxchg_32.h           |  4 ++--
 arch/sparc/include/asm/cmpxchg_64.h           |  6 +++---
 arch/sparc/kernel/uprobes.c                   |  7 ++-----
 arch/xtensa/include/asm/cmpxchg.h             |  4 ++--
 drivers/gpu/drm/i915/gt/intel_engine_cs.c     |  2 +-
 .../gpu/drm/i915/gt/intel_engine_heartbeat.c  |  4 ++--
 .../drm/i915/gt/intel_execlists_submission.c  |  4 ++--
 drivers/gpu/drm/i915/gt/intel_ggtt.c          |  4 ++--
 drivers/gpu/drm/i915/gt/intel_gsc.c           |  2 +-
 drivers/gpu/drm/i915/gt/intel_gt.c            |  4 ++--
 drivers/gpu/drm/i915/gt/intel_gt_pm.c         |  2 +-
 drivers/gpu/drm/i915/gt/intel_lrc.c           |  6 +++---
 drivers/gpu/drm/i915/gt/intel_migrate.c       |  2 +-
 drivers/gpu/drm/i915/gt/intel_rc6.c           |  2 +-
 drivers/gpu/drm/i915/gt/intel_rps.c           |  2 +-
 drivers/gpu/drm/i915/gt/selftest_context.c    |  2 +-
 .../drm/i915/gt/selftest_ring_submission.c    |  2 +-
 drivers/gpu/drm/i915/gt/selftest_timeline.c   |  2 +-
 drivers/gpu/drm/i915/gt/uc/intel_gsc_uc.c     |  2 +-
 drivers/gpu/drm/i915/gt/uc/intel_uc.c         |  2 +-
 drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c      |  2 +-
 drivers/gpu/drm/i915/i915_utils.h             |  1 +
 include/linux/llist.h                         |  6 ++----
 include/linux/non-atomic/xchg.h               | 19 +++++++++++++++++++
 include/linux/qed/qed_chain.h                 | 19 +++++++------------
 io_uring/io_uring.c                           |  7 ++-----
 io_uring/slist.h                              |  6 ++----
 51 files changed, 126 insertions(+), 155 deletions(-)
 create mode 100644 include/linux/non-atomic/xchg.h
  

Hi,

Ping on the series.
Arnd, Andrew is there anything more I can do to push the process forward?

Regards
Andrzej


On 18.01.2023 16:35, Andrzej Hajda wrote:
> Hi all,
> 
> The helper is tiny and there are advices we can live without it, so
> I want to present few arguments why it would be good to have it:
> 
> 1. Code readability/simplification/number of lines:
>    - decreases number of lines,
>    - it often eliminates local variables,
>    - for real examples see patches 3+.
> 
> 2. Presence of similar helpers in other somehow related languages/libs:
> 
> a) Rust[1]: 'replace' from std::mem module, there is also 'take'
>      helper (__xchg(&x, 0)), which is the same as private helper in
>      i915 - fetch_and_zero, see latest patch.
> b) C++ [2]: 'exchange' from utility header.
> 
> If the idea is OK there are still 2 questions to answer:
> 
> 1. Name of the helper, __xchg follows kernel conventions,
>      but for me Rust names are also OK.
> 2. Where to put the helper:
> a) as in this patchset include/linux/non-atomic/xchg.h,
>      proposed by Andy Shevchenko,
> b) include/linux/utils.h ? any better name? Some kind
>      of container for simple helpers.
> 
> All __xchg conversions were performed using cocci script,
> then manually adjusted if necessary.
> 
> There is lot of places it can be used in, I have just chosen
> some of them. I can provide cocci script to detect others (not all),
> if necessary.
> 
> Changes:
> v2: squashed all __xchg -> __arch_xchg t one patch (Arnd)
> v3: fixed alpha/xchg_local (lkp@intel.com)
> v4: adjusted indentation (Heiko)
> v5: added more __xchg conversions - patches 3-6, added tags
> 
> [1]: https://doc.rust-lang.org/std/mem/index.html
> [2]: https://en.cppreference.com/w/cpp/header/utility
> 
> Regards
> Andrzej
> 
> Andrzej Hajda (7):
>    arch: rename all internal names __xchg to __arch_xchg
>    linux/include: add non-atomic version of xchg
>    arch/*/uprobes: simplify arch_uretprobe_hijack_return_addr
>    llist: simplify __llist_del_all
>    io_uring: use __xchg if possible
>    qed: use __xchg if possible
>    drm/i915/gt: use __xchg instead of internal helper
> 
>   arch/alpha/include/asm/cmpxchg.h              | 10 +++++-----
>   arch/arc/include/asm/cmpxchg.h                |  4 ++--
>   arch/arm/include/asm/cmpxchg.h                |  7 ++++---
>   arch/arm/probes/uprobes/core.c                |  8 ++------
>   arch/arm64/include/asm/cmpxchg.h              |  7 +++----
>   arch/arm64/kernel/probes/uprobes.c            |  9 ++-------
>   arch/csky/kernel/probes/uprobes.c             |  9 ++-------
>   arch/hexagon/include/asm/cmpxchg.h            | 10 +++++-----
>   arch/ia64/include/asm/cmpxchg.h               |  2 +-
>   arch/ia64/include/uapi/asm/cmpxchg.h          |  4 ++--
>   arch/loongarch/include/asm/cmpxchg.h          |  4 ++--
>   arch/m68k/include/asm/cmpxchg.h               |  6 +++---
>   arch/mips/include/asm/cmpxchg.h               |  4 ++--
>   arch/mips/kernel/uprobes.c                    | 10 ++--------
>   arch/openrisc/include/asm/cmpxchg.h           | 10 +++++-----
>   arch/parisc/include/asm/cmpxchg.h             |  4 ++--
>   arch/powerpc/include/asm/cmpxchg.h            |  4 ++--
>   arch/powerpc/kernel/uprobes.c                 | 10 ++--------
>   arch/riscv/include/asm/atomic.h               |  2 +-
>   arch/riscv/include/asm/cmpxchg.h              |  4 ++--
>   arch/riscv/kernel/probes/uprobes.c            |  9 ++-------
>   arch/s390/include/asm/cmpxchg.h               |  8 ++++----
>   arch/s390/kernel/uprobes.c                    |  7 ++-----
>   arch/sh/include/asm/cmpxchg.h                 |  4 ++--
>   arch/sparc/include/asm/cmpxchg_32.h           |  4 ++--
>   arch/sparc/include/asm/cmpxchg_64.h           |  6 +++---
>   arch/sparc/kernel/uprobes.c                   |  7 ++-----
>   arch/xtensa/include/asm/cmpxchg.h             |  4 ++--
>   drivers/gpu/drm/i915/gt/intel_engine_cs.c     |  2 +-
>   .../gpu/drm/i915/gt/intel_engine_heartbeat.c  |  4 ++--
>   .../drm/i915/gt/intel_execlists_submission.c  |  4 ++--
>   drivers/gpu/drm/i915/gt/intel_ggtt.c          |  4 ++--
>   drivers/gpu/drm/i915/gt/intel_gsc.c           |  2 +-
>   drivers/gpu/drm/i915/gt/intel_gt.c            |  4 ++--
>   drivers/gpu/drm/i915/gt/intel_gt_pm.c         |  2 +-
>   drivers/gpu/drm/i915/gt/intel_lrc.c           |  6 +++---
>   drivers/gpu/drm/i915/gt/intel_migrate.c       |  2 +-
>   drivers/gpu/drm/i915/gt/intel_rc6.c           |  2 +-
>   drivers/gpu/drm/i915/gt/intel_rps.c           |  2 +-
>   drivers/gpu/drm/i915/gt/selftest_context.c    |  2 +-
>   .../drm/i915/gt/selftest_ring_submission.c    |  2 +-
>   drivers/gpu/drm/i915/gt/selftest_timeline.c   |  2 +-
>   drivers/gpu/drm/i915/gt/uc/intel_gsc_uc.c     |  2 +-
>   drivers/gpu/drm/i915/gt/uc/intel_uc.c         |  2 +-
>   drivers/gpu/drm/i915/gt/uc/intel_uc_fw.c      |  2 +-
>   drivers/gpu/drm/i915/i915_utils.h             |  1 +
>   include/linux/llist.h                         |  6 ++----
>   include/linux/non-atomic/xchg.h               | 19 +++++++++++++++++++
>   include/linux/qed/qed_chain.h                 | 19 +++++++------------
>   io_uring/io_uring.c                           |  7 ++-----
>   io_uring/slist.h                              |  6 ++----
>   51 files changed, 126 insertions(+), 155 deletions(-)
>   create mode 100644 include/linux/non-atomic/xchg.h
>
  

On Wed, Jan 18, 2023 at 04:35:22PM +0100, Andrzej Hajda wrote:

> Andrzej Hajda (7):
>   arch: rename all internal names __xchg to __arch_xchg
>   linux/include: add non-atomic version of xchg
>   arch/*/uprobes: simplify arch_uretprobe_hijack_return_addr
>   llist: simplify __llist_del_all
>   io_uring: use __xchg if possible
>   qed: use __xchg if possible
>   drm/i915/gt: use __xchg instead of internal helper

Nothing crazy in here I suppose, I somewhat wonder why you went through
the trouble, but meh.

You want me to take this through te locking tree (for the next cycle,
not this one) where I normally take atomic things or does someone else
want this?
  

On 22.02.2023 18:04, Peter Zijlstra wrote:
> On Wed, Jan 18, 2023 at 04:35:22PM +0100, Andrzej Hajda wrote:
> 
>> Andrzej Hajda (7):
>>    arch: rename all internal names __xchg to __arch_xchg
>>    linux/include: add non-atomic version of xchg
>>    arch/*/uprobes: simplify arch_uretprobe_hijack_return_addr
>>    llist: simplify __llist_del_all
>>    io_uring: use __xchg if possible
>>    qed: use __xchg if possible
>>    drm/i915/gt: use __xchg instead of internal helper
> 
> Nothing crazy in here I suppose, I somewhat wonder why you went through
> the trouble, but meh.

If you are asking why I have proposed this patchset, then the answer is 
simple, 1st I've tried to find a way to move internal i915 helper to 
core (see patch 7).
Then I was looking for possible other users of this helper. And 
apparently there are many of them, patches 3-7 shows some.


> 
> You want me to take this through te locking tree (for the next cycle,
> not this one) where I normally take atomic things or does someone else
> want this?

If you could take it I will be happy.

Regards
Andrzej
  

On Thu, Feb 23, 2023 at 10:24:19PM +0100, Andrzej Hajda wrote:
> On 22.02.2023 18:04, Peter Zijlstra wrote:
> > On Wed, Jan 18, 2023 at 04:35:22PM +0100, Andrzej Hajda wrote:
> > 
> > > Andrzej Hajda (7):
> > >    arch: rename all internal names __xchg to __arch_xchg
> > >    linux/include: add non-atomic version of xchg
> > >    arch/*/uprobes: simplify arch_uretprobe_hijack_return_addr
> > >    llist: simplify __llist_del_all
> > >    io_uring: use __xchg if possible
> > >    qed: use __xchg if possible
> > >    drm/i915/gt: use __xchg instead of internal helper
> > 
> > Nothing crazy in here I suppose, I somewhat wonder why you went through
> > the trouble, but meh.
> 
> If you are asking why I have proposed this patchset, then the answer is
> simple, 1st I've tried to find a way to move internal i915 helper to core
> (see patch 7).
> Then I was looking for possible other users of this helper. And apparently
> there are many of them, patches 3-7 shows some.
> 
> 
> > 
> > You want me to take this through te locking tree (for the next cycle,
> > not this one) where I normally take atomic things or does someone else
> > want this?
> 
> If you could take it I will be happy.

OK, I'll go queue it in tip/locking/core after -rc1. Thanks!