[PATCH v2 RFC 2/3] documentation: Add long atomic examples to memory-barriers.txt

Paul E. McKenney
2013-11-21T21:31:43Z

From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

Although the atomic_long_t functions are quite useful, they are a bit
obscure. This commit therefore adds the common ones alongside their
atomic_t counterparts in Documentation/memory-barriers.txt.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
---
Documentation/memory-barriers.txt | 24 +++++++++++++-----------
1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index 1c3c1d025f20..2170dcbedfaf 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -1728,21 +1728,23 @@ explicit lock operations, described later). These include:

xchg();
cmpxchg();
- atomic_xchg();
- atomic_cmpxchg();
- atomic_inc_return();
- atomic_dec_return();
- atomic_add_return();
- atomic_sub_return();
- atomic_inc_and_test();
- atomic_dec_and_test();
- atomic_sub_and_test();
- atomic_add_negative();
- atomic_add_unless(); /* when succeeds (returns 1) */
+ atomic_xchg(); atomic_long_xchg();
+ atomic_cmpxchg(); atomic_long_cmpxchg();
+ atomic_inc_return(); atomic_long_inc_return();
+ atomic_dec_return(); atomic_long_dec_return();
+ atomic_add_return(); atomic_long_add_return();
+ atomic_sub_return(); atomic_long_sub_return();
+ atomic_inc_and_test(); atomic_long_inc_and_test();
+ atomic_dec_and_test(); atomic_long_dec_and_test();
+ atomic_sub_and_test(); atomic_long_sub_and_test();
+ atomic_add_negative(); atomic_long_add_negative();
test_and_set_bit();
test_and_clear_bit();
test_and_change_bit();

+ /* when succeeds (returns 1) */
+ atomic_add_unless(); atomic_long_add_unless();
+
These are used for such things as implementing LOCK-class and UNLOCK-class
operations and adjusting reference counters towards object destruction, and as
such the implicit memory barrier effects are necessary.
--
1.8.1.5