From 040129002138af4e9cde953bf2b682ee5b9a1b74 Mon Sep 17 00:00:00 2001
From: vraatikka <vilho.raatikka@skysql.com>
Date: Thu, 22 Aug 2013 10:42:18 +0300
Subject: [PATCH] Added spinlock ses_lock to struct SESSION to ensure that for
 each session closeSession is called only once. closeSession is called from
 mysql_backend.c:gw_read_backend_event, and from dcb.c:dcb_close.

This is part of Bug #163.
---
 server/core/dcb.c                       | 26 +++++++++++++---
 server/core/session.c                   |  1 +
 server/include/session.h                |  3 ++
 server/modules/protocol/mysql_backend.c | 41 ++++++++++++++++++-------
 4 files changed, 56 insertions(+), 15 deletions(-)

diff --git a/server/core/dcb.c b/server/core/dcb.c
index 474579d59..0c358ad4a 100644
--- a/server/core/dcb.c
+++ b/server/core/dcb.c
@@ -611,11 +611,29 @@ dcb_close(DCB *dcb)
 		 */
 		SERVICE *service = dcb->session->service;
 
-		if (service && service->router && dcb->session->router_session)
+		if (service != NULL &&
+                    service->router != NULL &&
+                    dcb->session->router_session != NULL)
 		{
-			service->router->closeSession(
-                                service->router_instance,
-                                dcb->session->router_session);
+                        void* rsession = NULL;                
+                        /**
+                         * Protect call of closeSession.
+                         */
+                        spinlock_acquire(&dcb->session->ses_lock);
+                        rsession = dcb->session->router_session;
+                        dcb->session->router_session = NULL;
+                        spinlock_release(&dcb->session->ses_lock);
+
+                        if (rsession != NULL) {
+                                service->router->closeSession(
+                                        service->router_instance,
+                                        rsession);
+                        } else {
+                                skygw_log_write_flush(
+                                        LOGFILE_TRACE,
+                                        "%lu [dcb_close] rsession was NULL in dcb_close.",
+                                        pthread_self());
+                        }
 		}
 		session_free(dcb->session);
 	}
diff --git a/server/core/session.c b/server/core/session.c
index 9a6bc796d..f48e6872d 100644
--- a/server/core/session.c
+++ b/server/core/session.c
@@ -59,6 +59,7 @@ SESSION 	*session;
 
 	if ((session = (SESSION *)malloc(sizeof(SESSION))) == NULL)
 		return NULL;
+        spinlock_init(&session->ses_lock);
 	session->service = service;
 	session->client = client;
 	memset(&session->stats, 0, sizeof(SESSION_STATS));
diff --git a/server/include/session.h b/server/include/session.h
index d6fe7ed2d..c91b837bd 100644
--- a/server/include/session.h
+++ b/server/include/session.h
@@ -33,6 +33,8 @@
  * @endverbatim
  */
 #include <time.h>
+#include <atomic.h>
+#include <spinlock.h>
 
 struct dcb;
 struct service;
@@ -52,6 +54,7 @@ typedef struct {
  * and originating service together for the client session.
  */
 typedef struct session {
+        SPINLOCK        ses_lock;
 	int 		state;		/**< Current descriptor state */
 	struct dcb	*client;	/**< The client connection */
 	struct dcb	*backends;	/**< The set of backend servers */
diff --git a/server/modules/protocol/mysql_backend.c b/server/modules/protocol/mysql_backend.c
index ebef69258..65a9f51dd 100644
--- a/server/modules/protocol/mysql_backend.c
+++ b/server/modules/protocol/mysql_backend.c
@@ -145,7 +145,7 @@ static int gw_read_backend_event(DCB *dcb) {
                         current_session->user,
                         current_session->client_sha1,
                         backend_protocol);
-
+                
 		return 1;
 	}
 
@@ -163,13 +163,20 @@ static int gw_read_backend_event(DCB *dcb) {
                         router_instance = session->service->router_instance;
                         rsession = session->router_session;
 		}
-
 		/* read backed auth reply */
 		rv = gw_receive_backend_auth(backend_protocol);
 
 		switch (rv) {
 			case MYSQL_FAILED_AUTHENTICATION:
-				fprintf(stderr, ">>>> Backend Auth failed for user [%s], fd %i\n", current_session->user, dcb->fd);
+                                skygw_log_write_flush(
+                                        LOGFILE_ERROR,
+                                        "%lu [gw_read_backend_event] caught "
+                                        "MYSQL_FAILED_AUTHENTICATION from "
+                                        "gw_receive_backend_auth. Fd %d, user %s. "
+                                        "Closing the session.",
+                                        pthread_self(),
+                                        dcb->fd,
+                                        current_session->user);
 
 				backend_protocol->state = MYSQL_AUTH_FAILED;
 
@@ -179,18 +186,30 @@ static int gw_read_backend_event(DCB *dcb) {
                                         1,
                                         0,
                                         "Connection to backend lost right now");
-		
-				/* close the active session */		
-				router->closeSession(router_instance, rsession);
-
-				/* force the router_session to NULL
-				 * Later we will implement a proper status for the session
-				 */
-				session->router_session = NULL;
+                                /**
+                                 * Protect call of closeSession.
+                                 */
+                                spinlock_acquire(&session->ses_lock);
+                                rsession = session->router_session;
+                                session->router_session = NULL;
+                                spinlock_release(&session->ses_lock);
 
+                                if (rsession != NULL) {
+                                        /* close the active session */
+                                        router->closeSession(router_instance, rsession);
+                                }
 				return 1;
 
 			case MYSQL_SUCCESFUL_AUTHENTICATION:
+                                skygw_log_write_flush(
+                                        LOGFILE_TRACE,
+                                        "%lu [gw_read_backend_event] caught "
+                                        "MYSQL_SUCCESFUL_AUTHENTICATION from "
+                                        "gw_receive_backend_auth. Fd %d, user %s.",
+                                        pthread_self(),
+                                        dcb->fd,
+                                        current_session->user);
+
 				spinlock_acquire(&dcb->authlock);
 
 				backend_protocol->state = MYSQL_IDLE;