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Uros Bizjak
aef95dac9c
Commit:
6d12c8d308 ("percpu: Wire up cmpxchg128")
improved emulated cmpxchg8b_emu() library function to return
success/failure in a ZF flag.
Define arch_try_cmpxchg64() for !CONFIG_X86_CMPXCHG64 targets
to override the generic archy_try_cmpxchg() with an optimized
target specific implementation that handles ZF flag.
The assembly code at the call sites improves from:
bf56d: e8 fc ff ff ff call cmpxchg8b_emu
bf572: 8b 74 24 28 mov 0x28(%esp),%esi
bf576: 89 c3 mov %eax,%ebx
bf578: 89 d1 mov %edx,%ecx
bf57a: 8b 7c 24 2c mov 0x2c(%esp),%edi
bf57e: 89 f0 mov %esi,%eax
bf580: 89 fa mov %edi,%edx
bf582: 31 d8 xor %ebx,%eax
bf584: 31 ca xor %ecx,%edx
bf586: 09 d0 or %edx,%eax
bf588: 0f 84 e3 01 00 00 je bf771 <...>
to:
bf572: e8 fc ff ff ff call cmpxchg8b_emu
bf577: 0f 84 b6 01 00 00 je bf733 <...>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lore.kernel.org/r/20240408091547.90111-4-ubizjak@gmail.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
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In order to build the documentation, use ``make htmldocs`` or
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There are various text files in the Documentation/ subdirectory,
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Please read the Documentation/process/changes.rst file, as it contains the
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the problems which may result by upgrading your kernel.