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authorPaul E. McKenney <paulmck@us.ibm.com>2006-02-01 06:06:42 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2006-02-01 11:53:25 -0500
commitd19720a909b4443f78cbb03f4f090180e143ad9d (patch)
tree56e579612d82f4b30d5cb943df1079b0b5f4700a /Documentation/RCU/listRCU.txt
parent53d8be5c144ece5d48745810b14248968e73eaf2 (diff)
[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
232return holding the per-entry spinlock, as ipc_lock() does in fact do. 232return holding the per-entry spinlock, as ipc_lock() does in fact do.
233 233
234Quick Quiz: Why does the search function need to return holding the 234Quick Quiz: Why does the search function need to return holding the
235per-entry lock for this deleted-flag technique to be helpful? 235 per-entry lock for this deleted-flag technique to be helpful?
236 236
237If the system-call audit module were to ever need to reject stale data, 237If the system-call audit module were to ever need to reject stale data,
238one way to accomplish this would be to add a "deleted" flag and a "lock" 238one way to accomplish this would be to add a "deleted" flag and a "lock"
@@ -275,8 +275,8 @@ flag under the spinlock as follows:
275 { 275 {
276 struct audit_entry *e; 276 struct audit_entry *e;
277 277
278 /* Do not use the _rcu iterator here, since this is the only 278 /* Do not need to use the _rcu iterator here, since this
279 * deletion routine. */ 279 * is the only deletion routine. */
280 list_for_each_entry(e, list, list) { 280 list_for_each_entry(e, list, list) {
281 if (!audit_compare_rule(rule, &e->rule)) { 281 if (!audit_compare_rule(rule, &e->rule)) {
282 spin_lock(&e->lock); 282 spin_lock(&e->lock);
@@ -304,9 +304,12 @@ function to reject newly deleted data.
304 304
305 305
306Answer to Quick Quiz 306Answer to Quick Quiz
307 307 Why does the search function need to return holding the per-entry
308If the search function drops the per-entry lock before returning, then 308 lock for this deleted-flag technique to be helpful?
309the caller will be processing stale data in any case. If it is really 309
310OK to be processing stale data, then you don't need a "deleted" flag. 310 If the search function drops the per-entry lock before returning,
311If processing stale data really is a problem, then you need to hold the 311 then the caller will be processing stale data in any case. If it
312per-entry lock across all of the code that uses the value looked up. 312 is really OK to be processing stale data, then you don't need a
313 "deleted" flag. If processing stale data really is a problem,
314 then you need to hold the per-entry lock across all of the code
315 that uses the value that was returned.