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Commit f84cfbb0 authored by Chris Metcalf's avatar Chris Metcalf Committed by Paul E. McKenney
Browse files

Documentation/memory-barriers.txt: Fix ACCESS_ONCE thinko 



In commit 2ecf8101 ("Documentation/memory-barriers.txt: Add
needed ACCESS_ONCE() calls to memory-barriers.txt") the statement
"Q = P" was converted to "ACCESS_ONCE(Q) = P".  This should have
been "Q = ACCESS_ONCE(P)".  It later became "WRITE_ONCE(Q, P)".
This doesn't match the following text, which is "Q = LOAD P".
Change the statement to be "Q = READ_ONCE(P)".

Signed-off-by: default avatarChris Metcalf <cmetcalf@ezchip.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent c64c4b0f

Documentation/memory-barriers.txt

+4 −4
Original line number Diff line number Diff line
@@ -194,7 +194,7 @@ There are some minimal guarantees that may be expected of a CPU: 
 (*) On any given CPU, dependent memory accesses will be issued in order, with

     respect to itself.  This means that for:



	WRITE_ONCE(Q, P); smp_read_barrier_depends(); D = READ_ONCE(*Q);

	Q = READ_ONCE(P); smp_read_barrier_depends(); D = READ_ONCE(*Q);



     the CPU will issue the following memory operations:
@@ -202,9 +202,9 @@ There are some minimal guarantees that may be expected of a CPU: 


     and always in that order.  On most systems, smp_read_barrier_depends()

     does nothing, but it is required for DEC Alpha.  The READ_ONCE()

     and WRITE_ONCE() are required to prevent compiler mischief.  Please

     note that you should normally use something like rcu_dereference()

     instead of open-coding smp_read_barrier_depends().

     is required to prevent compiler mischief.  Please note that you

     should normally use something like rcu_dereference() instead of

     open-coding smp_read_barrier_depends().



 (*) Overlapping loads and stores within a particular CPU will appear to be

     ordered within that CPU.  This means that for: