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Commit 0e4bd2ab authored by Paul E. McKenney's avatar Paul E. McKenney
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documentation: Remove obsolete reference to RCU-protected indexes 



Commit #1ebee801 (rcu: Eliminate array-index-based RCU primitives)
eliminated the primitives supporting RCU-protected array indexes, but
failed to update Documentation/memory-barriers.txt accordingly.  This
commit therefore removes the discussion of RCU-protected array indexes.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 895f5542

Documentation/memory-barriers.txt

+0 −15
Original line number Diff line number Diff line
@@ -565,21 +565,6 @@ odd-numbered bank is idle, one can see the new value of the pointer P (&B), 
but the old value of the variable B (2).





Another example of where data dependency barriers might be required is where a

number is read from memory and then used to calculate the index for an array

access:



	CPU 1		      CPU 2

	===============	      ===============

	{ M[0] == 1, M[1] == 2, M[3] = 3, P == 0, Q == 3 }

	M[1] = 4;

	<write barrier>

	WRITE_ONCE(P, 1);

			      Q = READ_ONCE(P);

			      <data dependency barrier>

			      D = M[Q];





The data dependency barrier is very important to the RCU system,

for example.  See rcu_assign_pointer() and rcu_dereference() in

include/linux/rcupdate.h.  This permits the current target of an RCU'd