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authorPaul E. McKenney <paulmck@us.ibm.com>2006-02-01 03:06:42 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-02-01 08:53:25 -0800
commitd19720a909b4443f78cbb03f4f090180e143ad9d (patch)
tree56e579612d82f4b30d5cb943df1079b0b5f4700a /Documentation/RCU/listRCU.txt
parent53d8be5c144ece5d48745810b14248968e73eaf2 (diff)
downloadlinux-linaro-stable-d19720a909b4443f78cbb03f4f090180e143ad9d.tar.gz
[PATCH] RCU documentation fixes (January 2006 update)
Updates to in-tree RCU documentation based on comments over the past few months. 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/listRCU.txt')
-rw-r--r--Documentation/RCU/listRCU.txt21
1 files changed, 12 insertions, 9 deletions
diff --git a/Documentation/RCU/listRCU.txt b/Documentation/RCU/listRCU.txt
index f8a54fa0d8ab..1fd175368a87 100644
--- a/Documentation/RCU/listRCU.txt
+++ b/Documentation/RCU/listRCU.txt
@@ -232,7 +232,7 @@ entry does not exist. For this to be helpful, the search function must
return holding the per-entry spinlock, as ipc_lock() does in fact do.
Quick Quiz: Why does the search function need to return holding the
-per-entry lock for this deleted-flag technique to be helpful?
+ per-entry lock for this deleted-flag technique to be helpful?
If the system-call audit module were to ever need to reject stale data,
one way to accomplish this would be to add a "deleted" flag and a "lock"
@@ -275,8 +275,8 @@ flag under the spinlock as follows:
{
struct audit_entry *e;
- /* Do not use the _rcu iterator here, since this is the only
- * deletion routine. */
+ /* Do not need to use the _rcu iterator here, since this
+ * is the only deletion routine. */
list_for_each_entry(e, list, list) {
if (!audit_compare_rule(rule, &e->rule)) {
spin_lock(&e->lock);
@@ -304,9 +304,12 @@ function to reject newly deleted data.
Answer to Quick Quiz
-
-If the search function drops the per-entry lock before returning, then
-the caller will be processing stale data in any case. If it is really
-OK to be processing stale data, then you don't need a "deleted" flag.
-If processing stale data really is a problem, then you need to hold the
-per-entry lock across all of the code that uses the value looked up.
+ Why does the search function need to return holding the per-entry
+ lock for this deleted-flag technique to be helpful?
+
+ If the search function drops the per-entry lock before returning,
+ then the caller will be processing stale data in any case. If it
+ is really OK to be processing stale data, then you don't need a
+ "deleted" flag. If processing stale data really is a problem,
+ then you need to hold the per-entry lock across all of the code
+ that uses the value that was returned.