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f56810c94c
Use __this_cpu_try_cmpxchg() instead of __this_cpu_cmpxchg (*ptr, old,
new) == old in preload_this_cpu_lock(). x86 CMPXCHG instruction returns
success in ZF flag, so this change saves a compare after cmpxchg.
The generated code improves from:
4bb6: 48 85 f6 test %rsi,%rsi
4bb9: 0f 84 10 fa ff ff je 45cf <...>
4bbf: 4c 89 e8 mov %r13,%rax
4bc2: 65 48 0f b1 35 00 00 cmpxchg %rsi,%gs:0x0(%rip)
4bc9: 00 00
4bcb: 48 85 c0 test %rax,%rax
4bce: 0f 84 fb f9 ff ff je 45cf <...>
to:
4bb6: 48 85 f6 test %rsi,%rsi
4bb9: 0f 84 10 fa ff ff je 45cf <...>
4bbf: 4c 89 e8 mov %r13,%rax
4bc2: 65 48 0f b1 35 00 00 cmpxchg %rsi,%gs:0x0(%rip)
4bc9: 00 00
4bcb: 0f 84 fe f9 ff ff je 45cf <...>
No functional change intended.
Link: https://lkml.kernel.org/r/20240528144345.5980-2-ubizjak@gmail.com
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.