Documentation/memory-barriers.txt: fix important typo re memory barriers

Examples introducing neccesity of RMB+WMP pair reads as

        A=3	READ B
        www	rrrrrr
        B=4	READ A

Note the opposite order of reads vs writes.

But the first example without barriers reads as

        A=3	READ A
        B=4	READ B

There are 4 outcomes in the first example.

But if someone new to the concept tries to insert barriers like this:

        A=3	READ A
        www	rrrrrr
        B=4	READ B

he will still get all 4 possible outcomes, because "READ A" is first.

All this can be utterly confusing because barrier pair seems to be
superfluous.  In short, fixup first example to match latter examples
with barriers.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index 46412bded104ba14176c3323c48a2791c163a6ee..f1dc4a2155933874df9d30776c7aba220d7239be 100644 (file)
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -115,8 +115,8 @@ For example, consider the following sequence of events:
        CPU 1           CPU 2
        =============== ===============
        { A == 1; B == 2 }
-       A = 3;          x = A;
-       B = 4;          y = B;
+       A = 3;          x = B;
+       B = 4;          y = A;
 
 The set of accesses as seen by the memory system in the middle can be arranged
 in 24 different combinations: