[DRBD-cvs] svn commit by phil - r2914 - branches/drbd-8.0/drbd - Fixes a race condition in receive_state(), that was poi

[drbd-cvs at lists.linbit.com]

Author: phil
Date: 2007-06-05 09:29:24 +0200 (Tue, 05 Jun 2007)
New Revision: 2914

Modified:
   branches/drbd-8.0/drbd/drbd_receiver.c
Log:
Fixes a race condition in receive_state(), that was pointed out
by Ernest Montrose.


Modified: branches/drbd-8.0/drbd/drbd_receiver.c
===================================================================
--- branches/drbd-8.0/drbd/drbd_receiver.c	2007-06-04 11:22:39 UTC (rev 2913)
+++ branches/drbd-8.0/drbd/drbd_receiver.c	2007-06-05 07:29:24 UTC (rev 2914)
@@ -2390,7 +2390,7 @@
 STATIC int receive_state(drbd_dev *mdev, Drbd_Header *h)
 {
 	Drbd_State_Packet *p = (Drbd_State_Packet*)h;
-	drbd_conns_t nconn;
+	drbd_conns_t nconn,oconn;
 	drbd_state_t os,ns,peer_state;
 	int rv;
 
@@ -2398,12 +2398,16 @@
 	if (drbd_recv(mdev, h->payload, h->length) != h->length)
 		return FALSE;
 
-	nconn = mdev->state.conn;
+	peer_state.i = be32_to_cpu(p->state);
+
+	spin_lock_irq(&mdev->req_lock);
+ retry:
+	oconn = nconn = mdev->state.conn;
+	spin_unlock_irq(&mdev->req_lock);
+
 	if (nconn == WFReportParams ) nconn = Connected;
 
-	peer_state.i = be32_to_cpu(p->state);
-
-	if (mdev->p_uuid && mdev->state.conn <= Connected &&
+	if (mdev->p_uuid && oconn <= Connected &&
 	    inc_local_if_state(mdev,Negotiating) &&
 	    peer_state.disk >= Negotiating) {
 		nconn=drbd_sync_handshake(mdev,peer_state.role,peer_state.disk);
@@ -2412,19 +2416,8 @@
 		if(nconn == conn_mask) return FALSE;
 	}
 
-	if (mdev->state.conn > WFReportParams ) {
-		if( nconn > Connected && peer_state.conn <= Connected) {
-			// we want resync, peer has not yet decided to sync...
-			drbd_send_uuids(mdev);
-			drbd_send_state(mdev);
-		}
-		else if (nconn == Connected && peer_state.disk == Negotiating) {
-			// peer is waiting for us to respond...
-			drbd_send_state(mdev);
-		}
-	}
-
 	spin_lock_irq(&mdev->req_lock);
+	if( mdev->state.conn != oconn ) goto retry;
 	os = mdev->state;
 	ns.i = mdev->state.i;
 	ns.conn = nconn;
@@ -2446,6 +2439,18 @@
 		return FALSE;
 	}
 
+	if (oconn > WFReportParams ) {
+		if( nconn > Connected && peer_state.conn <= Connected) {
+			// we want resync, peer has not yet decided to sync...
+			drbd_send_uuids(mdev);
+			drbd_send_state(mdev);
+		}
+		else if (nconn == Connected && peer_state.disk == Negotiating) {
+			// peer is waiting for us to respond...
+			drbd_send_state(mdev);
+		}
+	}
+
 	mdev->net_conf->want_lose = 0;
 
 	/* FIXME assertion for (gencounts do not diverge) */