commit 754e801826207fb0c5ff490bbd8c36eb134aae5e
author Holger Hans Peter Freyther <zecke@selfish.org> Fri Apr 09 21:53:35 2010 +0200
committer Holger Hans Peter Freyther <zecke@selfish.org> Sat Apr 10 00:00:15 2010 +0200
tree f0a9b52d256e409dac0c24d7f1b7ba2fcec6ac13
parent 19722d44116353c14de8cb1f09eb45b9f8ec8ae2

[paging] Simplify the last request and treat llist as a queue

The current code was overly complex. It tried to iterate over
the list in a round robin and we had to keep track of the last
element, see if we remove that one, check if the list becomes
empty... This can all replaced by treating the double linked
list as a queue. We take the item at the front, do something
on it and then and then put it back to the list at the end.

openbsc/src/paging.c

diff --git a/openbsc/src/paging.c b/openbsc/src/paging.c
index 2ae3fc6..ece71ca 100644
--- a/openbsc/src/paging.c
+++ b/openbsc/src/paging.c
@@ -70,14 +70,6 @@
 static void paging_remove_request(struct gsm_bts_paging_state *paging_bts,
 				struct gsm_paging_request *to_be_deleted)
 {
-	/* Update the last_request if that is necessary */
-	if (to_be_deleted == paging_bts->last_request) {
-		paging_bts->last_request =
-			(struct gsm_paging_request *)paging_bts->last_request->entry.next;
-		if (&to_be_deleted->entry == &paging_bts->pending_requests)
-			paging_bts->last_request = NULL;
-	}
-
 	bsc_del_timer(&to_be_deleted->T3113);
 	llist_del(&to_be_deleted->entry);
 	subscr_put(to_be_deleted->subscr);
@@ -103,14 +95,6 @@
 			request->chan_type);
 }
 
-static void paging_move_to_next(struct gsm_bts_paging_state *paging_bts)
-{
-	paging_bts->last_request =
-		(struct gsm_paging_request *)paging_bts->last_request->entry.next;
-	if (&paging_bts->last_request->entry == &paging_bts->pending_requests)
-		paging_bts->last_request = NULL;
-}
-
 /*
  * This is kicked by the periodic PAGING LOAD Indicator
  * coming from abis_rsl.c
@@ -128,7 +112,6 @@
 	 * return then.
 	 */
 	if (llist_empty(&paging_bts->pending_requests)) {
-		paging_bts->last_request = NULL;
 		/* since the list is empty, no need to reschedule the timer */
 		return;
 	}
@@ -147,12 +130,8 @@
 		paging_bts->available_slots = 20;
 	}
 
-	if (!paging_bts->last_request)
-		paging_bts->last_request =
-			(struct gsm_paging_request *)paging_bts->pending_requests.next;
-
-	assert(paging_bts->last_request);
-	initial_request = paging_bts->last_request;
+	initial_request = llist_entry(paging_bts->pending_requests.next,
+				      struct gsm_paging_request, entry);
 	current_request = initial_request;
 
 	do {
@@ -160,17 +139,13 @@
 		page_ms(current_request);
 		paging_bts->available_slots--;
 
-		/*
-		 * move to the next item. We might wrap around
-		 * this means last_request will be NULL and we just
-		 * call paging_page_to_next again. It it guranteed
-		 * that the list is not empty.
-		 */
-		paging_move_to_next(paging_bts);
-		if (!paging_bts->last_request)
-			paging_bts->last_request =
-				(struct gsm_paging_request *)paging_bts->pending_requests.next;
-		current_request = paging_bts->last_request;
+		/* take the current and add it to the back */
+		llist_del(&current_request->entry);
+		llist_add_tail(&current_request->entry, &paging_bts->pending_requests);
+
+		/* take the next request */
+		current_request = llist_entry(paging_bts->pending_requests.next,
+					      struct gsm_paging_request, entry);
 	} while (paging_bts->available_slots > 0
 		    &&  initial_request != current_request);