lkml.org 
[lkml]   [2020]   [Mar]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[RFC][PATCH v2 6/8] x86: don't reload after cmpxchg in unsafe_atomic_op2() loop
Date
From: Al Viro <viro@zeniv.linux.org.uk>

lock cmpxchg leaves the current value in eax; no need to reload it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
arch/x86/include/asm/futex.h | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/futex.h b/arch/x86/include/asm/futex.h
index 53c07ab63762..d5d36f408ad0 100644
--- a/arch/x86/include/asm/futex.h
+++ b/arch/x86/include/asm/futex.h
@@ -34,17 +34,17 @@ do { \
do { \
int oldval = 0, ret, tem; \
asm volatile("1:\tmovl %2, %0\n" \
- "\tmovl\t%0, %3\n" \
+ "2:\tmovl\t%0, %3\n" \
"\t" insn "\n" \
- "2:\t" LOCK_PREFIX "cmpxchgl %3, %2\n" \
- "\tjnz\t1b\n" \
- "3:\n" \
+ "3:\t" LOCK_PREFIX "cmpxchgl %3, %2\n" \
+ "\tjnz\t2b\n" \
+ "4:\n" \
"\t.section .fixup,\"ax\"\n" \
- "4:\tmov\t%5, %1\n" \
+ "5:\tmov\t%5, %1\n" \
"\tjmp\t3b\n" \
"\t.previous\n" \
- _ASM_EXTABLE_UA(1b, 4b) \
- _ASM_EXTABLE_UA(2b, 4b) \
+ _ASM_EXTABLE_UA(1b, 5b) \
+ _ASM_EXTABLE_UA(3b, 5b) \
: "=&a" (oldval), "=&r" (ret), \
"+m" (*uaddr), "=&r" (tem) \
: "r" (oparg), "i" (-EFAULT), "1" (0)); \
--
2.11.0
\
 
 \ /
  Last update: 2020-03-27 03:29    [W:0.063 / U:0.056 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site