[PATCH] Documentation/memory-barriers.txt: fix ACCESS_ONCE thinko
From: Chris Metcalf
Date: Mon Nov 23 2015 - 17:04:34 EST
In commit 2ecf810121c7 ("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: Chris Metcalf <cmetcalf@xxxxxxxxxx>
Documentation/memory-barriers.txt | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index aef9487303d0..85304ebd187c 100644
@@ -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:
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