Commit-ID: 1de6e56ddc043437d335ee0455a1b34b73510c91
Gitweb: http://git.kernel.org/tip/1de6e56ddc043437d335ee0455a1b34b73510c91
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Tue, 29 Sep 2015 09:45:00 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Fri, 4 Dec 2015 12:26:50 -0800
rcu: Clarify role of ->expmaskinitnext
Analogy with the ->qsmaskinitnext field might lead one to believe that
->expmaskinitnext tracks online CPUs. This belief is incorrect: Any CPU
that has ever been online will have its bit set in the ->expmaskinitnext
field. This commit therefore adds a comment to make this clear, at
least to people who read comments.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index f32bebb..8151971 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -178,6 +178,8 @@ struct rcu_node {
/* beginning of each expedited GP. */
unsigned long expmaskinitnext;
/* Online CPUs for next expedited GP. */
+ /* Any CPU that has ever been online will */
+ /* have its bit set. */
unsigned long grpmask; /* Mask to apply to parent qsmask. */
/* Only one bit will be set in this mask. */
int grplo; /* lowest-numbered CPU or group here. */
--
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