kpriv/linux-hardened
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

Documentation/memory-barriers: Fix typos

Browse source 
Signed-off-by: SeongJae Park <sjpark@amazon.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
SeongJae Park 2020-01-31 21:52:37 +01:00 committed by Paul E. McKenney
parent 9671f30ee2
commit 8149b5cbfa
1 changed files with 4 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
Documentation/memory-barriers.txt
View file

@ -185,7 +185,7 @@ As a further example, consider this sequence of events:
=============== ===============
{ A == 1, B == 2, C == 3, P == &A, Q == &C }
B = 4; Q = P;
P = &B D = *Q;
P = &B; D = *Q;
There is an obvious data dependency here, as the value loaded into D depends on
the address retrieved from P by CPU 2. At the end of the sequence, any of the
@ -569,7 +569,7 @@ following sequence of events:
{ A == 1, B == 2, C == 3, P == &A, Q == &C }
B = 4;
<write barrier>
WRITE_ONCE(P, &B)
WRITE_ONCE(P, &B);
Q = READ_ONCE(P);
D = *Q;
@ -1721,7 +1721,7 @@ of optimizations:
and WRITE_ONCE() are more selective: With READ_ONCE() and
WRITE_ONCE(), the compiler need only forget the contents of the
indicated memory locations, while with barrier() the compiler must
discard the value of all memory locations that it has currented
discard the value of all memory locations that it has currently
cached in any machine registers. Of course, the compiler must also
respect the order in which the READ_ONCE()s and WRITE_ONCE()s occur,
though the CPU of course need not do so.
@ -1833,7 +1833,7 @@ Aside: In the case of data dependencies, the compiler would be expected
to issue the loads in the correct order (eg. `a[b]` would have to load
the value of b before loading a[b]), however there is no guarantee in
the C specification that the compiler may not speculate the value of b
(eg. is equal to 1) and load a before b (eg. tmp = a[1]; if (b != 1)
(eg. is equal to 1) and load a[b] before b (eg. tmp = a[1]; if (b != 1)
tmp = a[b]; ). There is also the problem of a compiler reloading b after
having loaded a[b], thus having a newer copy of b than a[b]. A consensus
has not yet been reached about these problems, however the READ_ONCE()