Commit 615cc2c9 authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Linus Torvalds

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: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0b07cb82
...@@ -115,8 +115,8 @@ For example, consider the following sequence of events: ...@@ -115,8 +115,8 @@ For example, consider the following sequence of events:
CPU 1 CPU 2 CPU 1 CPU 2
=============== =============== =============== ===============
{ A == 1; B == 2 } { A == 1; B == 2 }
A = 3; x = A; A = 3; x = B;
B = 4; y = B; B = 4; y = A;
The set of accesses as seen by the memory system in the middle can be arranged The set of accesses as seen by the memory system in the middle can be arranged
in 24 different combinations: in 24 different combinations:
......
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