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Commit fb2b5819 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
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Documentation/memory-barriers.txt: Add long atomic examples to memory-barriers.txt 



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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
Reviewed-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <linux-arch@vger.kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1386799151-2219-2-git-send-email-paulmck@linux.vnet.ibm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 2ecf8101

Documentation/memory-barriers.txt

+13 −11
Original line number Diff line number Diff line
@@ -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.