[Cluster-devel] GPF in dlm_lowcomms_stop

[David Teigland <teigland@redhat.com>]

On Wed, Mar 21, 2012 at 07:59:13PM -0600, dann frazier wrote:
> However... we've dropped the connections_lock, so its possible that a
> new connection gets created on line 9. This connection structure would
> have pointers to the workqueues that we're about to destroy. Sometime
> later on we get data on this new connection, we try to add work to the
> now-obliterated workqueues, and things blow up.

Hi Dan, I'm not very familiar with this code either, but I've talked with
Chrissie and she suggested we try something like this:

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index 133ef6d..a3c431e 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -142,6 +142,7 @@ struct writequeue_entry {
 
 static struct sockaddr_storage *dlm_local_addr[DLM_MAX_ADDR_COUNT];
 static int dlm_local_count;
+static int dlm_allow_conn;
 
 /* Work queues */
 static struct workqueue_struct *recv_workqueue;
@@ -710,6 +711,13 @@ static int tcp_accept_from_sock(struct connection *con)
 	struct connection *newcon;
 	struct connection *addcon;
 
+	mutex_lock(&connections_lock);
+	if (!dlm_allow_conn) {
+		mutex_unlock(&connections_lock);
+		return -1;
+	}
+	mutex_unlock(&connections_lock);
+
 	memset(&peeraddr, 0, sizeof(peeraddr));
 	result = sock_create_kern(dlm_local_addr[0]->ss_family, SOCK_STREAM,
 				  IPPROTO_TCP, &newsock);
@@ -1503,6 +1511,7 @@ void dlm_lowcomms_stop(void)
 	   socket activity.
 	*/
 	mutex_lock(&connections_lock);
+	dlm_allow_conn = 0;
 	foreach_conn(stop_conn);
 	mutex_unlock(&connections_lock);
 
@@ -1540,6 +1549,8 @@ int dlm_lowcomms_start(void)
 	if (!con_cache)
 		goto out;
 
+	dlm_allow_conn = 1;
+
 	/* Start listening */
 	if (dlm_config.ci_protocol == 0)
 		error = tcp_listen_for_all();
@@ -1555,6 +1566,7 @@ int dlm_lowcomms_start(void)
 	return 0;
 
 fail_unlisten:
+	dlm_allow_conn = 0;
 	con = nodeid2con(0,0);
 	if (con) {
 		close_connection(con, false);