On 10/13/2011 10:35 PM, Harsh Prateek Bora wrote:
+#define QLIST_INSERT_HEAD_RCU(head, elm, field) do { \
+ (elm)->field.le_prev =&(head)->lh_first; \
+ smp_wmb(); \
+ if (((elm)->field.le_next = (head)->lh_first) != NULL) \
+ (head)->lh_first->field.le_prev =&(elm)->field.le_next;\
+ smp_wmb(); \
+ (head)->lh_first = (elm); \
+ smp_wmb(); \
+} while (/* CONSTCOND*/0)
Actually, looking more at it it should be more like
(elm)->field.le_prev =&(head)->lh_first;
(elm)->field.le_next = (head)->lh_first;
smb_wmb(); /* fill elm before linking it */
if ((head)->lh_first != NULL)
(head)->lh_first->field.le_prev =&(elm)->field.le_next;
(head)->lh_first = (elm);
smp_wmb();
... which even saves a memory barrier.
Paolo
