Messages in this thread Patch in this message | | | From | Al Viro <> | Subject | [RFC][PATCH v2 6/8] x86: don't reload after cmpxchg in unsafe_atomic_op2() loop | Date | Fri, 27 Mar 2020 02:28:34 +0000 |
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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
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