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-rw-r--r--Documentation/RCU/checklist.txt2
-rw-r--r--Documentation/RCU/rcuref.txt16
-rw-r--r--Documentation/RCU/whatisRCU.txt2
3 files changed, 9 insertions, 11 deletions
diff --git a/Documentation/RCU/checklist.txt b/Documentation/RCU/checklist.txt
index cf5562cbe356..6e253407b3dc 100644
--- a/Documentation/RCU/checklist.txt
+++ b/Documentation/RCU/checklist.txt
@@ -210,7 +210,7 @@ over a rather long period of time, but improvements are always welcome!
number of updates per grace period.
9. All RCU list-traversal primitives, which include
- rcu_dereference(), list_for_each_rcu(), list_for_each_entry_rcu(),
+ rcu_dereference(), list_for_each_entry_rcu(),
list_for_each_continue_rcu(), and list_for_each_safe_rcu(),
must be either within an RCU read-side critical section or
must be protected by appropriate update-side locks. RCU
diff --git a/Documentation/RCU/rcuref.txt b/Documentation/RCU/rcuref.txt
index 451de2ad8329..4202ad093130 100644
--- a/Documentation/RCU/rcuref.txt
+++ b/Documentation/RCU/rcuref.txt
@@ -29,9 +29,9 @@ release_referenced() delete()
}
If this list/array is made lock free using RCU as in changing the
-write_lock() in add() and delete() to spin_lock and changing read_lock
-in search_and_reference to rcu_read_lock(), the atomic_get in
-search_and_reference could potentially hold reference to an element which
+write_lock() in add() and delete() to spin_lock() and changing read_lock()
+in search_and_reference() to rcu_read_lock(), the atomic_inc() in
+search_and_reference() could potentially hold reference to an element which
has already been deleted from the list/array. Use atomic_inc_not_zero()
in this scenario as follows:
@@ -40,20 +40,20 @@ add() search_and_reference()
{ {
alloc_object rcu_read_lock();
... search_for_element
- atomic_set(&el->rc, 1); if (atomic_inc_not_zero(&el->rc)) {
- write_lock(&list_lock); rcu_read_unlock();
+ atomic_set(&el->rc, 1); if (!atomic_inc_not_zero(&el->rc)) {
+ spin_lock(&list_lock); rcu_read_unlock();
return FAIL;
add_element }
... ...
- write_unlock(&list_lock); rcu_read_unlock();
+ spin_unlock(&list_lock); rcu_read_unlock();
} }
3. 4.
release_referenced() delete()
{ {
- ... write_lock(&list_lock);
+ ... spin_lock(&list_lock);
if (atomic_dec_and_test(&el->rc)) ...
call_rcu(&el->head, el_free); delete_element
- ... write_unlock(&list_lock);
+ ... spin_unlock(&list_lock);
} ...
if (atomic_dec_and_test(&el->rc))
call_rcu(&el->head, el_free);
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index e04d643a9f57..96170824a717 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -786,8 +786,6 @@ RCU pointer/list traversal:
list_for_each_entry_rcu
hlist_for_each_entry_rcu
- list_for_each_rcu (to be deprecated in favor of
- list_for_each_entry_rcu)
list_for_each_continue_rcu (to be deprecated in favor of new
list_for_each_entry_continue_rcu)