Additional spinlock in random_jkiss. Initial attempt at implementing dummy sessions to provide total consistency - used in mysql_client in relation to authentication - a single static dummy session is used and linked from the client dcb when authentication is not yet complete.

server/core/dcb.c

@@ -346,9 +346,12 @@ dcb_final_free(DCB *dcb)
 				local_session->client = NULL;
 				spinlock_release(&local_session->ses_lock);
 			}
+                        if (SESSION_STATE_DUMMY != local_session->state)
+                        {
                             session_free(local_session);
                         }
 		}
+	}
 
 	if (dcb->protocol && (!DCB_IS_CLONE(dcb)))
 		free(dcb->protocol);

server/core/random_jkiss.c

@@ -117,11 +117,13 @@ static void
 random_init_jkiss(void)
 {
     int newrand, i;
+    spinlock_acquire(&random_jkiss_spinlock);
     if ((newrand = random_jkiss_devrand()) != 0) x = newrand;
     if ((newrand = random_jkiss_devrand()) != 0) y = newrand;
     if ((newrand = random_jkiss_devrand()) != 0) z = newrand;
     if ((newrand = random_jkiss_devrand()) != 0) 
         c = newrand % 698769068 + 1; /* Should be less than 698769069 */
+    spinlock_release(&random_jkiss_spinlock);
     
     /* "Warm up" our random number generator */
     for (i = 0; i < 100; i++) random_jkiss();

server/core/session.c

@@ -56,6 +56,7 @@ static size_t session_id;
 static SPINLOCK	session_spin = SPINLOCK_INIT;
 static SESSION	*allSessions = NULL;
 
+static struct session session_dummy_struct;
 
 static int session_setup_filters(SESSION *session);
 static void session_simple_free(SESSION *session, DCB *dcb);
@@ -212,6 +213,48 @@ session_alloc(SERVICE *service, DCB *client_dcb)
     return session;
 }
 
+/**
+ * Allocate a dummy session so that DCBs can always have sessions.
+ *
+ * Only one dummy session exists, it is statically declared
+ * 
+ * @param client_dcb	The client side DCB
+ * @return		The dummy created session
+ */
+SESSION *
+session_alloc_dummy(DCB *client_dcb)
+{
+    SESSION 	*session;
+    
+    session = &session_dummy_struct;
+#if defined(SS_DEBUG)
+    session->ses_chk_top = CHK_NUM_SESSION;
+    session->ses_chk_tail = CHK_NUM_SESSION;
+#endif
+    session->ses_is_child = false;
+    spinlock_init(&session->ses_lock);
+    session->service = NULL;
+    session->client = NULL;
+    session->n_filters = 0;
+    memset(&session->stats, 0, sizeof(SESSION_STATS));
+    session->stats.connect = 0;
+    session->state = SESSION_STATE_DUMMY;
+    /*<
+     * Associate the session to the client DCB and set the reference count on
+     * the session to indicate that there is a single reference to the
+     * session. There is no need to protect this or use atomic add as the
+     * session has not been made available to the other threads at this
+     * point.
+     */
+    session->data = NULL;
+    session->refcount = 1;
+    session->ses_id = 0; 
+    session->next = NULL;
+
+    client_dcb->session = session;
+    return session;
+}
+
 /**
  * Enable specified logging for the current session and increase logger 
  * counter.
@@ -323,6 +366,10 @@ session_simple_free(SESSION *session, DCB *dcb)
     }
     if (session)
     {
+        if (SESSION_STATE_DUMMY == session->state)
+        {
+            return;
+        }
         if (session && session->router_session)
         {
             session->service->router->freeSession(
@@ -344,6 +391,10 @@ session_simple_free(SESSION *session, DCB *dcb)
 bool
 session_free(SESSION *session)
 {
+    if (session && SESSION_STATE_DUMMY == session->state)
+    {
+        return true;
+    }
         CHK_SESSION(session);
         
         /*
@@ -711,6 +762,8 @@ session_state(int state)
 	{
 	case SESSION_STATE_ALLOC:
 		return "Session Allocated";
+	case SESSION_STATE_DUMMY:
+		return "Dummy Session";
 	case SESSION_STATE_READY:
 		return "Session Ready";
 	case SESSION_STATE_ROUTER_READY:

server/include/session.h

@@ -64,7 +64,8 @@ typedef enum {
     SESSION_STATE_LISTENER,         /*< for listener session */
     SESSION_STATE_LISTENER_STOPPED, /*< for listener session */
     SESSION_STATE_TO_BE_FREED,	    /*< ready to be freed as soon as there are no references */
-    SESSION_STATE_FREE              /*< for all sessions */
+    SESSION_STATE_FREE,             /*< for all sessions */
+    SESSION_STATE_DUMMY             /*< dummy session for consistency */
 } session_state_t;
 
 /**
@@ -162,6 +163,7 @@ typedef struct session {
 
 SESSION *get_all_sessions();
 SESSION	*session_alloc(struct service *, struct dcb *);
+SESSION	*session_alloc_dummy(struct dcb *);
 bool    session_free(SESSION *);
 int	session_isvalid(SESSION *);
 int	session_reply(void *inst, void *session, GWBUF *data);

server/modules/protocol/mysql_backend.c

@@ -140,7 +140,7 @@ static MYSQL_session* gw_get_shared_session_auth_info(
 
         spinlock_acquire(&dcb->session->ses_lock);
 
-        if (dcb->session->state != SESSION_STATE_ALLOC) { 
+        if (dcb->session->state != SESSION_STATE_ALLOC && dcb->session->state != SESSION_STATE_DUMMY) { 
                 auth_info = dcb->session->data;
         } else {
                 LOGIF(LE, (skygw_log_write_flush(

server/modules/protocol/mysql_client.c

@@ -912,7 +912,7 @@ int gw_read_client_event(
 			if (session != NULL) 
 			{
 				CHK_SESSION(session);
-				ss_dassert(session->state != SESSION_STATE_ALLOC);
+				ss_dassert(session->state != SESSION_STATE_ALLOC && session->state != SESSION_STATE_DUMMY);
 				
 				protocol->protocol_auth_state = MYSQL_IDLE;
 				/** 
@@ -1012,7 +1012,7 @@ int gw_read_client_event(
 		if (session != NULL)
 		{
 		    CHK_SESSION(session);
-		    ss_dassert(session->state != SESSION_STATE_ALLOC);
+		    ss_dassert(session->state != SESSION_STATE_ALLOC && session->state != SESSION_STATE_DUMMY);
 
 		    protocol->protocol_auth_state = MYSQL_IDLE;
 		    /**
@@ -1643,6 +1643,7 @@ int gw_MySQLAccept(DCB *listener)
 		}
 
                 client_dcb->service = listener->session->service;
+                client_dcb->session = session_alloc_dummy(client_dcb);
                 client_dcb->fd = c_sock;
 
 		// get client address

utils/skygw_debug.h

@@ -210,6 +210,7 @@ typedef enum skygw_chk_t {
                              ((s) == DCB_STATE_UNDEFINED ? "DCB_STATE_UNDEFINED" : "DCB_STATE_UNKNOWN")))))))
 
 #define STRSESSIONSTATE(s) ((s) == SESSION_STATE_ALLOC ? "SESSION_STATE_ALLOC" : \
+                            ((s) == SESSION_STATE_DUMMY ? "SESSION_STATE_DUMMY" : \
                              ((s) == SESSION_STATE_READY ? "SESSION_STATE_READY" : \
                               ((s) == SESSION_STATE_LISTENER ? "SESSION_STATE_LISTENER" : \
                                ((s) == SESSION_STATE_LISTENER_STOPPED ? "SESSION_STATE_LISTENER_STOPPED" : \