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authorUros Bizjak <ubizjak@gmail.com>2022-08-22 16:38:51 +0200
committerAndrew Morton <akpm@linux-foundation.org>2022-09-11 21:55:09 -0700
commite1d7c7609ae0933b59840390c1b207ac0a925c8b (patch)
tree55170982bc11f6e761a136a01649c1ccc5e92d1b /include/linux/bitops.h
parent21490eff121555b123f7088b935e40ee43d2c642 (diff)
bitops: use try_cmpxchg in set_mask_bits and bit_clear_unless
Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in set_mask_bits and bit_clear_unless. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Also, try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg fails, enabling further code simplifications. Link: https://lkml.kernel.org/r/20220822143851.3290-1-ubizjak@gmail.com Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'include/linux/bitops.h')
-rw-r--r--include/linux/bitops.h11
1 files changed, 6 insertions, 5 deletions
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 3b89c64bcfd8..fb24a513d917 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -328,10 +328,10 @@ static __always_inline void __assign_bit(long nr, volatile unsigned long *addr,
const typeof(*(ptr)) mask__ = (mask), bits__ = (bits); \
typeof(*(ptr)) old__, new__; \
\
+ old__ = READ_ONCE(*(ptr)); \
do { \
- old__ = READ_ONCE(*(ptr)); \
new__ = (old__ & ~mask__) | bits__; \
- } while (cmpxchg(ptr, old__, new__) != old__); \
+ } while (!try_cmpxchg(ptr, &old__, new__)); \
\
old__; \
})
@@ -343,11 +343,12 @@ static __always_inline void __assign_bit(long nr, volatile unsigned long *addr,
const typeof(*(ptr)) clear__ = (clear), test__ = (test);\
typeof(*(ptr)) old__, new__; \
\
+ old__ = READ_ONCE(*(ptr)); \
do { \
- old__ = READ_ONCE(*(ptr)); \
+ if (old__ & test__) \
+ break; \
new__ = old__ & ~clear__; \
- } while (!(old__ & test__) && \
- cmpxchg(ptr, old__, new__) != old__); \
+ } while (!try_cmpxchg(ptr, &old__, new__)); \
\
!(old__ & test__); \
})