[PATCH] rcu: small rcu_dereference doc update

Milos Vyletel
2015-04-17T10:34:03Z

Make a note stating that repeated calls of rcu_dereference() may not
return the same pointer if update happens while in critical section.

Reported-by: Jeff Haran <jeff.haran@citrix.com>
Signed-off-by: Milos Vyletel <milos@redhat.com>
---
Documentation/RCU/whatisRCU.txt | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index 88dfce1..82b1b2c 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -256,7 +256,9 @@ rcu_dereference()
If you are going to be fetching multiple fields from the
RCU-protected structure, using the local variable is of
course preferred. Repeated rcu_dereference() calls look
- ugly and incur unnecessary overhead on Alpha CPUs.
+ ugly, do not guarantee that same pointer will be returned
+ if update happened while in critical section and incur
+ unnecessary overhead on Alpha CPUs.

Note that the value returned by rcu_dereference() is valid
only within the enclosing RCU read-side critical section.
--
2.1.0