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Merge tag 'lkmm.2023.10.28a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

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Pull Linux Kernel Memory Model updates from Paul McKenney:
 "This update adds paragraphs to the portions of memory-barriers.txt
  that have been marked historical due to changes in the way that the
  Linux kernel handles DEC Alpha. These paragraphs includes information
  on where to find the corresponding up-to-date information"

* tag 'lkmm.2023.10.28a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  docs: memory-barriers: Add note on compiler transformation and address deps
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Linus Torvalds
2023-10-30 17:54:43 -10:00
parent c9049984f0 1566bf4b13
commit 6750f0de53
1 changed files with 7 additions and 0 deletions
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7
Documentation/memory-barriers.txt
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@@ -396,6 +396,10 @@ 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.
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
@@ -556,6 +560,9 @@ 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.
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