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Subject[PATCH rcu 5/7] doc: Update rcu_access_pointer() advice in rcu_dereference.rst
Date
This commit updates the rcu_access_pointer() advice, noting that its
return value should not be assigned to a local variable, and also noting
that there is little point in using rcu_access_pointer() within an RCU
read-side critical section.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
Documentation/RCU/rcu_dereference.rst | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/Documentation/RCU/rcu_dereference.rst b/Documentation/RCU/rcu_dereference.rst
index 0b418a5b243c5..81e828c8313b8 100644
--- a/Documentation/RCU/rcu_dereference.rst
+++ b/Documentation/RCU/rcu_dereference.rst
@@ -128,10 +128,16 @@ Follow these rules to keep your RCU code working properly:
This sort of comparison occurs frequently when scanning
RCU-protected circular linked lists.

- Note that if checks for being within an RCU read-side
- critical section are not required and the pointer is never
- dereferenced, rcu_access_pointer() should be used in place
- of rcu_dereference().
+ Note that if the pointer comparison is done outside
+ of an RCU read-side critical section, and the pointer
+ is never dereferenced, rcu_access_pointer() should be
+ used in place of rcu_dereference(). In most cases,
+ it is best to avoid accidental dereferences by testing
+ the rcu_access_pointer() return value directly, without
+ assigning it to a variable.
+
+ Within an RCU read-side critical section, there is little
+ reason to use rcu_access_pointer().

- The comparison is against a pointer that references memory
that was initialized "a long time ago." The reason
--
2.31.1.189.g2e36527f23
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