Files
linux/lib
Uros Bizjak 4fbf8b136d locking/atomics: Use atomic_try_cmpxchg_release() to micro-optimize rcuref_put_slowpath()
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
2023-10-10 10:14:27 +02:00
..
2023-06-09 17:44:13 -07:00
2018-08-16 12:14:42 -07:00
2023-04-08 13:45:37 -07:00
2021-01-21 14:06:00 -07:00
2022-03-07 12:48:35 -07:00
2021-08-19 09:02:55 +09:00
2023-02-02 22:50:01 -08:00
2023-02-02 22:50:01 -08:00
2022-04-22 21:30:57 +02:00
2023-02-15 15:44:43 +01:00
2021-01-03 20:05:18 -05:00
2023-03-19 10:02:04 -07:00
2022-03-07 12:48:35 -07:00
2022-04-29 14:38:01 -07:00
2022-10-03 14:03:21 -07:00
2021-08-19 09:02:55 +09:00
2021-07-08 11:48:20 -07:00
2023-08-21 13:46:25 -07:00
2023-04-17 18:01:23 +02:00
2021-07-08 11:48:20 -07:00
2023-08-24 16:20:18 -07:00
2018-10-16 13:45:44 +02:00
2022-10-03 17:34:32 -07:00
2021-07-08 11:48:20 -07:00
2023-07-21 11:40:20 -06:00
2021-06-18 11:43:09 +02:00
2021-07-08 11:48:20 -07:00
2022-01-20 08:52:54 +02:00
2018-10-15 16:31:29 -04:00