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x86: don't reload after cmpxchg in unsafe_atomic_op2() loop

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

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2020-03-26 17:34:40 -04:00
parent 0ec33c0171
commit 8aef36dacb
1 changed files with 8 additions and 8 deletions
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16
arch/x86/include/asm/futex.h
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@ -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)); \