diff options
Diffstat (limited to 'Documentation/memory-barriers.txt')
| -rw-r--r-- | Documentation/memory-barriers.txt | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index 2ba8461b0631..41ffd7e9cdcf 100644 --- a/Documentation/memory-barriers.txt +++ b/Documentation/memory-barriers.txt @@ -637,7 +637,8 @@ as follows: b = p; /* BUG: Compiler and CPU can both reorder!!! */ Finally, the READ_ONCE_CTRL() includes an smp_read_barrier_depends() -that DEC Alpha needs in order to respect control depedencies. +that DEC Alpha needs in order to respect control depedencies. Alternatively +use one of atomic{,64}_read_ctrl(). So don't leave out the READ_ONCE_CTRL(). @@ -796,9 +797,9 @@ site: https://www.cl.cam.ac.uk/~pes20/ppcmem/index.html. In summary: - (*) Control dependencies must be headed by READ_ONCE_CTRL(). - Or, as a much less preferable alternative, interpose - smp_read_barrier_depends() between a READ_ONCE() and the + (*) Control dependencies must be headed by READ_ONCE_CTRL(), + atomic{,64}_read_ctrl(). Or, as a much less preferable alternative, + interpose smp_read_barrier_depends() between a READ_ONCE() and the control-dependent write. (*) Control dependencies can order prior loads against later stores. @@ -820,10 +821,10 @@ In summary: and WRITE_ONCE() can help to preserve the needed conditional. (*) Control dependencies require that the compiler avoid reordering the - dependency into nonexistence. Careful use of READ_ONCE_CTRL() - or smp_read_barrier_depends() can help to preserve your control - dependency. Please see the Compiler Barrier section for more - information. + dependency into nonexistence. Careful use of READ_ONCE_CTRL(), + atomic{,64}_read_ctrl() or smp_read_barrier_depends() can help to + preserve your control dependency. Please see the Compiler Barrier + section for more information. (*) Control dependencies pair normally with other types of barriers. |