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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-18 18:50:03 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-18 18:50:03 +0000
commit01a69402cf9d38ff180345d55c2ee51c7e89fbc7 (patch)
treeb406c5242a088c4f59c6e4b719b783f43aca6ae9 /Documentation/memory-barriers.txt
parentAdding upstream version 6.7.12. (diff)
downloadlinux-01a69402cf9d38ff180345d55c2ee51c7e89fbc7.tar.xz
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Adding upstream version 6.8.9.upstream/6.8.9
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'Documentation/memory-barriers.txt')
-rw-r--r--Documentation/memory-barriers.txt17
1 files changed, 10 insertions, 7 deletions
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index d414e145f..4202174a6 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -396,10 +396,11 @@ Memory barriers come in four basic varieties:
(2) Address-dependency barriers (historical).
- [!] This section is marked as HISTORICAL: For more up-to-date
- information, including how compiler transformations related to pointer
- comparisons can sometimes cause problems, see
- Documentation/RCU/rcu_dereference.rst.
+ [!] This section is marked as HISTORICAL: it covers the long-obsolete
+ smp_read_barrier_depends() macro, the semantics of which are now
+ implicit in all marked accesses. For more up-to-date information,
+ including how compiler transformations can sometimes break address
+ dependencies, see Documentation/RCU/rcu_dereference.rst.
An address-dependency barrier is a weaker form of read barrier. In the
case where two loads are performed such that the second depends on the
@@ -560,9 +561,11 @@ There are certain things that the Linux kernel memory barriers do not guarantee:
ADDRESS-DEPENDENCY BARRIERS (HISTORICAL)
----------------------------------------
-[!] This section is marked as HISTORICAL: For more up-to-date information,
-including how compiler transformations related to pointer comparisons can
-sometimes cause problems, see Documentation/RCU/rcu_dereference.rst.
+[!] This section is marked as HISTORICAL: it covers the long-obsolete
+smp_read_barrier_depends() macro, the semantics of which are now implicit
+in all marked accesses. For more up-to-date information, including
+how compiler transformations can sometimes break address dependencies,
+see Documentation/RCU/rcu_dereference.rst.
As of v4.15 of the Linux kernel, an smp_mb() was added to READ_ONCE() for
DEC Alpha, which means that about the only people who need to pay attention