diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2023-09-18 20:40:27 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2023-09-18 22:18:32 +0200 |
| commit | a432b7c0cf420dbf2448c6bda6a6697afbb153d5 (patch) | |
| tree | 72c4cde8aeaa1b08a0bb1ea23ba040f9a358fcab /arch/x86/Kconfig | |
| parent | 6f23fc47c1b2ac226704fb7294f43ed3b0965e51 (diff) | |
locking/lockref/x86: Enable ARCH_USE_CMPXCHG_LOCKREF for X86_CMPXCHG64
The following commit:
bc08b449ee14 ("lockref: implement lockless reference count updates using cmpxchg()")
enabled lockless reference count updates using cmpxchg() only for x86_64,
and left x86_32 behind due to inability to detect support for
cmpxchg8b instruction.
Nowadays, we can use CONFIG_X86_CMPXCHG64 for this purpose. Also,
by using try_cmpxchg64() instead of cmpxchg64() in the CMPXCHG_LOOP macro,
the compiler actually produces sane code, improving the
lockref_get_not_zero() main loop from:
eb: 8d 48 01 lea 0x1(%eax),%ecx
ee: 85 c0 test %eax,%eax
f0: 7e 2f jle 121 <lockref_get_not_zero+0x71>
f2: 8b 44 24 10 mov 0x10(%esp),%eax
f6: 8b 54 24 14 mov 0x14(%esp),%edx
fa: 8b 74 24 08 mov 0x8(%esp),%esi
fe: f0 0f c7 0e lock cmpxchg8b (%esi)
102: 8b 7c 24 14 mov 0x14(%esp),%edi
106: 89 c1 mov %eax,%ecx
108: 89 c3 mov %eax,%ebx
10a: 8b 74 24 10 mov 0x10(%esp),%esi
10e: 89 d0 mov %edx,%eax
110: 31 fa xor %edi,%edx
112: 31 ce xor %ecx,%esi
114: 09 f2 or %esi,%edx
116: 75 58 jne 170 <lockref_get_not_zero+0xc0>
to:
350: 8d 4f 01 lea 0x1(%edi),%ecx
353: 85 ff test %edi,%edi
355: 7e 79 jle 3d0 <lockref_get_not_zero+0xb0>
357: f0 0f c7 0e lock cmpxchg8b (%esi)
35b: 75 53 jne 3b0 <lockref_get_not_zero+0x90>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20230918184050.9180-1-ubizjak@gmail.com
Diffstat (limited to 'arch/x86/Kconfig')
| -rw-r--r-- | arch/x86/Kconfig | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 66bfabae8814..1379603016fd 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -28,7 +28,6 @@ config X86_64 select ARCH_HAS_GIGANTIC_PAGE select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 select ARCH_SUPPORTS_PER_VMA_LOCK - select ARCH_USE_CMPXCHG_LOCKREF select HAVE_ARCH_SOFT_DIRTY select MODULES_USE_ELF_RELA select NEED_DMA_MAP_STATE @@ -118,6 +117,7 @@ config X86 select ARCH_SUPPORTS_LTO_CLANG select ARCH_SUPPORTS_LTO_CLANG_THIN select ARCH_USE_BUILTIN_BSWAP + select ARCH_USE_CMPXCHG_LOCKREF if X86_CMPXCHG64 select ARCH_USE_MEMTEST select ARCH_USE_QUEUED_RWLOCKS select ARCH_USE_QUEUED_SPINLOCKS |