Subject: [PATCH v2 0/5] locking: Introduce local{,64}_try_cmpxchg

From: Uros Bizjak <[email-masked]>
Date: Wed, 5 Apr 2023 16:17:05 +0200

Add generic and target specific support for local{,64}_try_cmpxchg
and wire up support for all targets that use local_t infrastructure.

The patch enables x86 targets to emit special instruction for
local_try_cmpxchg and also local64_try_cmpxchg for x86_64.

The last patch changes __perf_output_begin in events/ring_buffer
to use new locking primitive and improves code from

     4b3:	48 8b 82 e8 00 00 00 	mov    0xe8(%rdx),%rax
     4ba:	48 8b b8 08 04 00 00 	mov    0x408(%rax),%rdi
     4c1:	8b 42 1c             	mov    0x1c(%rdx),%eax
     4c4:	48 8b 4a 28          	mov    0x28(%rdx),%rcx
     4c8:	85 c0                	test   %eax,%eax
     ...
     4ef:	48 89 c8             	mov    %rcx,%rax
     4f2:	48 0f b1 7a 28       	cmpxchg %rdi,0x28(%rdx)
     4f7:	48 39 c1             	cmp    %rax,%rcx
     4fa:	75 b7                	jne    4b3 <...>

to

     4b2:	48 8b 4a 28          	mov    0x28(%rdx),%rcx
     4b6:	48 8b 82 e8 00 00 00 	mov    0xe8(%rdx),%rax
     4bd:	48 8b b0 08 04 00 00 	mov    0x408(%rax),%rsi
     4c4:	8b 42 1c             	mov    0x1c(%rdx),%eax
     4c7:	85 c0                	test   %eax,%eax
     ...
     4d4:	48 89 c8             	mov    %rcx,%rax
     4d7:	48 0f b1 72 28       	cmpxchg %rsi,0x28(%rdx)
     4dc:	0f 85 d0 00 00 00    	jne    5b2 <...>
     ...
     5b2:	48 89 c1             	mov    %rax,%rcx
     5b5:	e9 fc fe ff ff       	jmp    4b6 <...>

Please note that in addition to removed compare, the load from
0x28(%rdx) gets moved out of the loop and the code is rearranged
according to likely/unlikely tags in the source.
---
v2:

Implement target specific support for local_try_cmpxchg and
local_cmpxchg using typed C wrappers that call their _local
counterpart and provide additional checking of their input
arguments.

Cc: Richard Henderson <[email-masked]>
Cc: Ivan Kokshaysky <[email-masked]>
Cc: Matt Turner <[email-masked]>
Cc: Huacai Chen <[email-masked]>
Cc: WANG Xuerui <[email-masked]>
Cc: Thomas Bogendoerfer <[email-masked]>
Cc: Michael Ellerman <[email-masked]>
Cc: Nicholas Piggin <[email-masked]>
Cc: Christophe Leroy <[email-masked]>
Cc: Thomas Gleixner <[email-masked]>
Cc: Ingo Molnar <[email-masked]>
Cc: Borislav Petkov <[email-masked]>
Cc: Dave Hansen <[email-masked]>
Cc: "H. Peter Anvin" <[email-masked]>
Cc: Arnd Bergmann <[email-masked]>
Cc: Peter Zijlstra <[email-masked]>
Cc: Arnaldo Carvalho de Melo <[email-masked]>
Cc: Mark Rutland <[email-masked]>
Cc: Alexander Shishkin <[email-masked]>
Cc: Jiri Olsa <[email-masked]>
Cc: Namhyung Kim <[email-masked]>
Cc: Ian Rogers <[email-masked]>
Cc: Will Deacon <[email-masked]>
Cc: Boqun Feng <[email-masked]>
Cc: Jiaxun Yang <[email-masked]>
Cc: Jun Yi <[email-masked]>

Uros Bizjak (5):
  locking/atomic: Add generic try_cmpxchg{,64}_local support
  locking/generic: Wire up local{,64}_try_cmpxchg
  locking/arch: Wire up local_try_cmpxchg
  locking/x86: Define arch_try_cmpxchg_local
  events: Illustrate the transition to local{,64}_try_cmpxchg

 arch/alpha/include/asm/local.h              | 12 +++++++++--
 arch/loongarch/include/asm/local.h          | 13 +++++++++--
 arch/mips/include/asm/local.h               | 13 +++++++++--
 arch/powerpc/include/asm/local.h            | 11 ++++++++++
 arch/x86/events/core.c                      |  9 ++++----
 arch/x86/include/asm/cmpxchg.h              |  6 ++++++
 arch/x86/include/asm/local.h                | 13 +++++++++--
 include/asm-generic/local.h                 |  1 +
 include/asm-generic/local64.h               | 12 ++++++++++-
 include/linux/atomic/atomic-arch-fallback.h | 24 ++++++++++++++++++++-
 include/linux/atomic/atomic-instrumented.h  | 20 ++++++++++++++++-
 kernel/events/ring_buffer.c                 |  5 +++--
 scripts/atomic/gen-atomic-fallback.sh       |  4 ++++
 scripts/atomic/gen-atomic-instrumented.sh   |  2 +-
 14 files changed, 126 insertions(+), 19 deletions(-)

-- 
2.39.2