Cleanup the reader/writer policy in netgraph(4). Assign

either reader or writer flag on item in the function, that
allocates the item. Do not modify these flags when item is
applied or queued.
  The only exceptions are node and hook overrides - they can
change item flags to writer.

1 files changed, 25 insertions, 24 deletions

diff --git a/sys/netgraph/ng_base.c b/sys/netgraph/ng_base.c
index fa863db..893e19b 100644
--- a/sys/netgraph/ng_base.c
+++ b/sys/netgraph/ng_base.c
@@ -1972,7 +1972,6 @@ ng_acquire_read(struct ng_queue *ngq, item_p item)
 	/*
 	 * and queue the request for later.
 	 */
-	item->el_flags |= NGQF_READER;
 	ng_queue_rw(ngq, item, NGQRW_R);
 	if (CAN_GET_WORK(ngq->q_flags))
 		ng_setisr(ngq->q_node);
@@ -2005,7 +2004,6 @@ restart:
 	/*
 	 * and queue the request for later.
 	 */
-	item->el_flags &= ~NGQF_RW;
 	ng_queue_rw(ngq, item, NGQRW_W);
 	if (CAN_GET_WORK(ngq->q_flags))
 		ng_setisr(ngq->q_node);
@@ -2144,9 +2142,6 @@ ng_snd_item(item_p item, int flags)
 		if ((hook->hk_flags & HK_QUEUE)) {
 			queue = 1;
 		}
-		/* By default data is a reader in the locking scheme */
-		item->el_flags |= NGQF_READER;
-		rw = NGQRW_R;
 		break;
 	case NGQF_MESG:
 		/*
@@ -2159,34 +2154,38 @@ ng_snd_item(item_p item, int flags)
 		if (hook && (hook->hk_flags & HK_QUEUE)) {
 			queue = 1;
 		}
-		/* Data messages count as writers unles explicitly exempted */
-		if (NGI_MSG(item)->header.cmd & NGM_READONLY) {
-			item->el_flags |= NGQF_READER;
-			rw = NGQRW_R;
-		} else {
-			item->el_flags &= ~NGQF_RW;
-			rw = NGQRW_W;
-		}
 		break;
 	case NGQF_FN:
-		item->el_flags &= ~NGQF_RW;
-		rw = NGQRW_W;
 		break;
 	default:
 		NG_FREE_ITEM(item);
 		TRAP_ERROR();
 		return (EINVAL);
 	}
+	switch(item->el_flags & NGQF_RW) {
+	case NGQF_READER:
+		rw = NGQRW_R;
+		break;
+	case NGQF_WRITER:
+		rw = NGQRW_W;
+		break;
+	default:
+		panic("%s: invalid item flags %lx", __func__, item->el_flags);
+	}
+
 	/*
-	 * If the node specifies single threading, force writer semantics
-	 * Similarly the node may say one hook always produces writers.
-	 * These are over-rides.
+	 * If the node specifies single threading, force writer semantics.
+	 * Similarly, the node may say one hook always produces writers.
+	 * These are overrides. Modify the item itself, so that if it
+	 * is queued now, it would be dequeued later with corrected
+	 * read/write flags.
 	 */
 	if ((node->nd_flags & NGF_FORCE_WRITER)
-	|| (hook && (hook->hk_flags & HK_FORCE_WRITER))) {
+	    || (hook && (hook->hk_flags & HK_FORCE_WRITER))) {
 			rw = NGQRW_W;
 			item->el_flags &= ~NGQF_READER;
 	}
+
 	if (queue) {
 		/* Put it on the queue for that node*/
 #ifdef	NETGRAPH_DEBUG
@@ -3322,7 +3321,7 @@ ng_package_data(struct mbuf *m, int flags)
 		return (NULL);
 	}
 	ITEM_DEBUG_CHECKS;
-	item->el_flags = NGQF_DATA;
+	item->el_flags = NGQF_DATA | NGQF_READER;
 	item->el_next = NULL;
 	NGI_M(item) = m;
 	return (item);
@@ -3345,7 +3344,11 @@ ng_package_msg(struct ng_mesg *msg, int flags)
 		return (NULL);
 	}
 	ITEM_DEBUG_CHECKS;
-	item->el_flags = NGQF_MESG;
+	/* Messages items count as writers unless explicitly exempted. */
+	if (msg->header.cmd & NGM_READONLY)
+		item->el_flags = NGQF_MESG | NGQF_READER;
+	else
+		item->el_flags = NGQF_MESG | NGQF_WRITER;
 	item->el_next = NULL;
 	/*
 	 * Set the current lasthook into the queue item
@@ -3453,8 +3456,6 @@ ng_address_ID(node_p here, item_p item, ng_ID_t ID, ng_ID_t retaddr)
 		return(EINVAL);
 	}
 	/* Fill out the contents */
-	item->el_flags = NGQF_MESG;
-	item->el_next = NULL;
 	NGI_SET_NODE(item, dest);
 	NGI_CLR_HOOK(item);
 	SET_RETADDR(item, here, retaddr);
@@ -3482,7 +3483,7 @@ ng_package_msg_self(node_p here, hook_p hook, struct ng_mesg *msg)
 	}
 
 	/* Fill out the contents */
-	item->el_flags = NGQF_MESG;
+	item->el_flags = NGQF_MESG | NGQF_WRITER;
 	item->el_next = NULL;
 	NG_NODE_REF(here);
 	NGI_SET_NODE(item, here);