[tip: locking/core] x86: don't reload after cmpxchg in unsafe_atomic_op2() loop
From: tip-bot2 for Al Viro
Date: Sat Mar 28 2020 - 07:07:36 EST
The following commit has been merged into the locking/core branch of tip:
Commit-ID: 8aef36dacb3a932cb77da8bb7eb21a154babd0b8
Gitweb: https://git.kernel.org/tip/8aef36dacb3a932cb77da8bb7eb21a154babd0b8
Author: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
AuthorDate: Thu, 26 Mar 2020 17:34:40 -04:00
Committer: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
CommitterDate: Fri, 27 Mar 2020 23:58:54 -04:00
x86: don't reload after cmpxchg in unsafe_atomic_op2() loop
lock cmpxchg leaves the current value in eax; no need to reload it.
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/futex.h | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/arch/x86/include/asm/futex.h b/arch/x86/include/asm/futex.h
index 53c07ab..5ff7626 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" \
- "\tjmp\t3b\n" \
+ "5:\tmov\t%5, %1\n" \
+ "\tjmp\t4b\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)); \