rculfhash: document flags

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/rculfhash.c b/rculfhash.c
index 55f56ceb6bc54a248032d3e2ce94e2db1bfeb82b..e8147178ada51bc333c27237ac806311c8bc08a0 100644 (file)
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -53,6 +53,11 @@
 #define max(a, b)      ((a) > (b) ? (a) : (b))
 #endif
 
+/*
+ * The removed flag needs to be updated atomically with the pointer.
+ * The dummy flag does not require to be updated atomically with the
+ * pointer, but it is added as a pointer low bit flag to save space.
+ */
 #define REMOVED_FLAG           (1UL << 0)
 #define DUMMY_FLAG             (1UL << 1)
 #define FLAGS_MASK             ((1UL << 2) - 1)

diff --git a/urcu/rculfhash.h b/urcu/rculfhash.h
index 5c5d4eb1a57ad87a0b2ec8f7c10ed704efd6b66f..b98b4932922e02fab3cd53e6630a46ca3b848a06 100644 (file)
--- a/urcu/rculfhash.h
+++ b/urcu/rculfhash.h
@@ -9,7 +9,7 @@ extern "C" {
 #endif
 
 struct _rcu_ht_node {
-       struct rcu_ht_node *next;
+       struct rcu_ht_node *next;       /* ptr | DUMMY_FLAG | REMOVED_FLAG */
        unsigned long reverse_hash;
 };