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authorLinus Torvalds <torvalds@linux-foundation.org>2016-03-24 19:36:18 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-03-24 19:36:18 +0300
commit19d6f04cd374b886b98d7b070ebf287c93bff7ac (patch)
tree26414711c808fbfd736423dfd5b1498abb256b37 /include
parentaca04ce5dbda50758b813b1e3d710098991cfa9a (diff)
parentf75d48644c56a31731d17fa693c8175328957e1d (diff)
downloadlinux-19d6f04cd374b886b98d7b070ebf287c93bff7ac.tar.xz
Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Ingo Molnar: "Documentation updates and a bitops ordering fix" * 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: bitops: Do not default to __clear_bit() for __clear_bit_unlock() documentation: Clarify compiler store-fusion example documentation: Transitivity is not cumulativity documentation: Add alternative release-acquire outcome documentation: Distinguish between local and global transitivity documentation: Subsequent writes ordered by rcu_dereference() documentation: Remove obsolete reference to RCU-protected indexes documentation: Fix memory-barriers.txt section references documentation: Fix control dependency and identical stores
Diffstat (limited to 'include')
-rw-r--r--include/asm-generic/bitops/lock.h14
1 files changed, 7 insertions, 7 deletions
diff --git a/include/asm-generic/bitops/lock.h b/include/asm-generic/bitops/lock.h
index c30266e94806..8ef0ccbf8167 100644
--- a/include/asm-generic/bitops/lock.h
+++ b/include/asm-generic/bitops/lock.h
@@ -29,16 +29,16 @@ do { \
* @nr: the bit to set
* @addr: the address to start counting from
*
- * This operation is like clear_bit_unlock, however it is not atomic.
- * It does provide release barrier semantics so it can be used to unlock
- * a bit lock, however it would only be used if no other CPU can modify
- * any bits in the memory until the lock is released (a good example is
- * if the bit lock itself protects access to the other bits in the word).
+ * A weaker form of clear_bit_unlock() as used by __bit_lock_unlock(). If all
+ * the bits in the word are protected by this lock some archs can use weaker
+ * ops to safely unlock.
+ *
+ * See for example x86's implementation.
*/
#define __clear_bit_unlock(nr, addr) \
do { \
- smp_mb(); \
- __clear_bit(nr, addr); \
+ smp_mb__before_atomic(); \
+ clear_bit(nr, addr); \
} while (0)
#endif /* _ASM_GENERIC_BITOPS_LOCK_H_ */