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Use atomic_try_cmpxchg() instead of atomic_cmpxchg(*ptr, old, new) == old in rcuref_put_slowpath(). On x86 the CMPXCHG instruction returns success in the ZF flag, so this change saves a compare after CMPXCHG. Additionaly, the compiler reorders some code blocks to follow likely/unlikely annotations in the atomic_try_cmpxchg() macro, improving the code from: 9a: f0 0f b1 0b lock cmpxchg %ecx,(%rbx) 9e: 83 f8 ff cmp $0xffffffff,%eax a1: 74 04 je a7 <rcuref_put_slowpath+0x27> a3: 31 c0 xor %eax,%eax to: 9a: f0 0f b1 0b lock cmpxchg %ecx,(%rbx) 9e: 75 4c jne ec <rcuref_put_slowpath+0x6c> a0: b0 01 mov $0x1,%al No functional change intended. Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paul E. McKenney <paulmck@kernel.org> Link: https://lore.kernel.org/r/20230509150255.3691-1-ubizjak@gmail.com
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 Restructured Text 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.