locking/atomic/bitops: Document and clarify ordering semantics for failed test_and_...
authorWill Deacon <will.deacon@arm.com>
Tue, 13 Feb 2018 13:30:19 +0000 (13:30 +0000)
committerIngo Molnar <mingo@kernel.org>
Tue, 13 Feb 2018 13:55:53 +0000 (14:55 +0100)
commit61e02392d3c7ecac1f91c0a90a8043d67e081846
tree643df7dcf736a212690237f1b49ef108a2f096e6
parent11dc13224c975efcec96647a4768a6f1bb7a19a8
locking/atomic/bitops: Document and clarify ordering semantics for failed test_and_{}_bit()

A test_and_{}_bit() operation fails if the value of the bit is such that
the modification does not take place. For example, if test_and_set_bit()
returns 1. In these cases, follow the behaviour of cmpxchg and allow the
operation to be unordered. This also applies to test_and_set_bit_lock()
if the lock is found to be be taken already.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1518528619-20049-1-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Documentation/atomic_bitops.txt
include/asm-generic/bitops/lock.h