X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=urcu%2Frculfhash.h;h=de34fae0b424b20a0b7d7538932376209a603969;hb=13f656f996861f47172f34a1ef28e338616ff5e2;hp=de315265d38efd597e26a0c4d3938474196005df;hpb=c1888f3a47cf8f7c213269888ce42d191de7e34a;p=urcu.git

diff --git a/urcu/rculfhash.h b/urcu/rculfhash.h
index de31526..de34fae 100644
--- a/urcu/rculfhash.h
+++ b/urcu/rculfhash.h
@@ -39,8 +39,15 @@ extern "C" {
  * cds_lfht_node: Contains the next pointers and reverse-hash
  * value required for lookup and traversal of the hash table.
  *
- * struct cds_lfht_node should be aligned on 4-bytes boundaries because
- * the two lower bits are used as flags.
+ * struct cds_lfht_node should be aligned on 8-bytes boundaries because
+ * the three lower bits are used as flags. It is worth noting that the
+ * information contained within these three bits could be represented on
+ * two bits by re-using the same bit for REMOVAL_OWNER_FLAG and
+ * BUCKET_FLAG. This can be done if we ensure that no iterator nor
+ * updater check the BUCKET_FLAG after it detects that the REMOVED_FLAG
+ * is set. Given the minimum size of struct cds_lfht_node is 8 bytes on
+ * 32-bit architectures, we choose to go for simplicity and reserve
+ * three bits.
  *
  * struct cds_lfht_node can be embedded into a structure (as a field).
  * caa_container_of() can be used to get the structure from the struct
@@ -51,9 +58,9 @@ extern "C" {
  * of the hash value for cds_lfht APIs.
  */
 struct cds_lfht_node {
-	struct cds_lfht_node *next;	/* ptr | BUCKET_FLAG | REMOVED_FLAG */
+	struct cds_lfht_node *next;	/* ptr | REMOVAL_OWNER_FLAG | BUCKET_FLAG | REMOVED_FLAG */
 	unsigned long reverse_hash;
-} __attribute__((aligned(4)));
+} __attribute__((aligned(8)));
 
 /* cds_lfht_iter: Used to track state while traversing a hash chain. */
 struct cds_lfht_iter {