urcu-call-rcu: use wait-free splice return value

We can now use the splice return value to know if the source queue was
empty rather than testing for destination queue emptiness after the
splice operation.

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

diff --git a/urcu-call-rcu-impl.h b/urcu-call-rcu-impl.h
index 5dfdb9277b5a351f62d09ee7b534f94c0a4ca3b5..6580397b1ee42b04a8e48b5c29a76220ea39b6d0 100644 (file)
--- a/urcu-call-rcu-impl.h
+++ b/urcu-call-rcu-impl.h
@@ -252,11 +252,14 @@ static void *call_rcu_thread(void *arg)
                struct cds_wfcq_head cbs_tmp_head;
                struct cds_wfcq_tail cbs_tmp_tail;
                struct cds_wfcq_node *cbs, *cbs_tmp_n;
+               enum cds_wfcq_ret splice_ret;
 
                cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail);
-               __cds_wfcq_splice_blocking(&cbs_tmp_head, &cbs_tmp_tail,
-                       &crdp->cbs_head, &crdp->cbs_tail);
-               if (!cds_wfcq_empty(&cbs_tmp_head, &cbs_tmp_tail)) {
+               splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head,
+                       &cbs_tmp_tail, &crdp->cbs_head, &crdp->cbs_tail);
+               assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK);
+               assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY);
+               if (splice_ret != CDS_WFCQ_RET_SRC_EMPTY) {
                        synchronize_rcu();
                        cbcount = 0;
                        __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head,