[PATCH] RCU: update docs to include kfree_rcu()

From: Kees Cook
Date: Fri Oct 19 2012 - 12:48:31 EST

Mention kfree_rcu() in the call_rcu() section. Additionally fix the
example code for list replacement that used the wrong structure element.

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Documentation/RCU/listRCU.txt | 2 +-
Documentation/RCU/whatisRCU.txt | 13 +++++++++++--
2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/Documentation/RCU/listRCU.txt b/Documentation/RCU/listRCU.txt
index 4349c14..adb5a37 100644
--- a/Documentation/RCU/listRCU.txt
+++ b/Documentation/RCU/listRCU.txt
@@ -205,7 +205,7 @@ RCU ("read-copy update") its name. The RCU code is as follows:
audit_copy_rule(&ne->rule, &e->rule);
ne->rule.action = newaction;
ne->rule.file_count = newfield_count;
- list_replace_rcu(e, ne);
+ list_replace_rcu(&e->list, &ne->list);
call_rcu(&e->rcu, audit_free_rule);
return 0;
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index bf0f6de..160ac55 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -499,6 +499,8 @@ The foo_reclaim() function might appear as follows:
struct foo *fp = container_of(rp, struct foo, rcu);

+ foo_cleanup(fp->a);

@@ -521,6 +523,12 @@ o Use call_rcu() -after- removing a data element from an
read-side critical sections that might be referencing that
data item.

+If the callback for call_rcu() is not doing anything more than calling
+kfree() on the structure, you can use kfree_rcu() instead of call_rcu()
+to avoid having to write your own callback:
+ kfree_rcu(old_fp, rcu);
Again, see checklist.txt for additional rules governing the use of RCU.

@@ -773,8 +781,8 @@ a single atomic update, converting to RCU will require special care.

Also, the presence of synchronize_rcu() means that the RCU version of
delete() can now block. If this is a problem, there is a callback-based
-mechanism that never blocks, namely call_rcu(), that can be used in
-place of synchronize_rcu().
+mechanism that never blocks, namely call_rcu() or kfree_rcu(), that can
+be used in place of synchronize_rcu().

@@ -813,6 +821,7 @@ RCU: Critical sections Grace period Barrier
rcu_read_unlock synchronize_rcu
rcu_dereference synchronize_rcu_expedited
+ kfree_rcu

bh: Critical sections Grace period Barrier

Kees Cook
Chrome OS Security
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