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authorPaul E. McKenney <paulmck@us.ibm.com>2006-06-25 05:48:44 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-25 10:01:17 -0700
commit165d6c78ee24127dde5c750b2af0a239f9c11d1a (patch)
treea9329b5b24893588114441f43d576dfa310e5f43 /Documentation/RCU/whatisRCU.txt
parent76d42bd96984832c4ea8bc8cbd74e496ac31409e (diff)
downloadlinux-linaro-stable-165d6c78ee24127dde5c750b2af0a239f9c11d1a.tar.gz
[PATCH] RCU documentation: self-limiting updates and call_rcu()
An update to the RCU documentation calling out the self-limiting-update-rate advantages of synchronize_rcu(), and describing how to use call_rcu() in a way that results in self-limiting updates. Self-limiting updates are important to avoiding RCU-induced OOM in face of denial-of-service attacks. Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'Documentation/RCU/whatisRCU.txt')
-rw-r--r--Documentation/RCU/whatisRCU.txt12
1 files changed, 11 insertions, 1 deletions
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index 6e459420ee9f..4f41a60e5111 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -184,7 +184,17 @@ synchronize_rcu()
blocking, it registers a function and argument which are invoked
after all ongoing RCU read-side critical sections have completed.
This callback variant is particularly useful in situations where
- it is illegal to block.
+ it is illegal to block or where update-side performance is
+ critically important.
+
+ However, the call_rcu() API should not be used lightly, as use
+ of the synchronize_rcu() API generally results in simpler code.
+ In addition, the synchronize_rcu() API has the nice property
+ of automatically limiting update rate should grace periods
+ be delayed. This property results in system resilience in face
+ of denial-of-service attacks. Code using call_rcu() should limit
+ update rate in order to gain this same sort of resilience. See
+ checklist.txt for some approaches to limiting the update rate.
rcu_assign_pointer()