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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2009-03-10 12:55:57 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-03-10 15:55:11 -0700
commit0612ea00a010e36fde61e7b7649a1105b0ef1080 (patch)
tree3e543336430dafbd67237075954f9ce0ccab2e65 /Documentation/RCU/checklist.txt
parentbe50b8342dead8cacf57d4839240106b225d31f5 (diff)
downloadlinux-linaro-stable-0612ea00a010e36fde61e7b7649a1105b0ef1080.tar.gz
rcu: documentation 1Q09 update
Update the RCU documentation to call out the need for callers of primitives like call_rcu() and synchronize_rcu() to prevent subsequent RCU readers from hazard. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/RCU/checklist.txt')
-rw-r--r--Documentation/RCU/checklist.txt12
1 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt
index 6e253407b3dc..accfe2f5247d 100644
--- a/Documentation/RCU/checklist.txt
+++ b/Documentation/RCU/checklist.txt
@@ -298,3 +298,15 @@ over a rather long period of time, but improvements are always welcome!
Note that, rcu_assign_pointer() and rcu_dereference() relate to
SRCU just as they do to other forms of RCU.
+
+15. The whole point of call_rcu(), synchronize_rcu(), and friends
+ is to wait until all pre-existing readers have finished before
+ carrying out some otherwise-destructive operation. It is
+ therefore critically important to -first- remove any path
+ that readers can follow that could be affected by the
+ destructive operation, and -only- -then- invoke call_rcu(),
+ synchronize_rcu(), or friends.
+
+ Because these primitives only wait for pre-existing readers,
+ it is the caller's responsibility to guarantee safety to
+ any subsequent readers.