Fixes possible crashes on threads management. Issue with volatile bool noticed by Bart Van Assche <bvanassche@acm.org>, great thanks!

git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@2052 d57e44dd-8a1f-0410-8b47-8ef2f437770f

scst/include/scst.h

@@ -1525,14 +1525,6 @@ struct scst_cmd_threads {
 
 	struct io_context *io_context; /* IO context of the threads pool */
 
-#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 25)
-	/*
-	 * Those kernels don't support ref counting based IO context sharing
-	 * between threads/processes, so need own ref counting.
-	 */
-	struct kref io_context_kref;
-#endif
-
 	bool io_context_ready;
 
 	int nr_threads; /* number of processing threads */
@@ -2177,6 +2169,7 @@ struct scst_thr_data_hdr {
  */
 struct scst_async_io_context_keeper {
 	struct kref aic_keeper_kref;
+	bool aic_ready;
 	struct io_context *aic;
 	struct task_struct *aic_keeper_thr;
 	wait_queue_head_t aic_keeper_waitQ;

scst/src/scst_lib.c

@@ -3004,7 +3004,7 @@ found:
 			t->acg_dev->acg->acg_io_grouping_type);
 	} else {
 		res = t;
-		if ((volatile bool)!res->active_cmd_threads->io_context_ready) {
+		if (!*(volatile bool*)&res->active_cmd_threads->io_context_ready) {
 			TRACE_MGMT_DBG("IO context for t %p not yet "
 				"initialized, waiting...", t);
 			msleep(100);
@@ -3056,9 +3056,7 @@ static int scst_ioc_keeper_thread(void *arg)
 
 	sBUG_ON(aic_keeper->aic != NULL);
 
-#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 19)
-	aic_keeper->aic = get_io_context(GFP_KERNEL);
-#else
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 25)
 	aic_keeper->aic = get_io_context(GFP_KERNEL, -1);
 #endif
 	TRACE_MGMT_DBG("Alloced new async IO context %p (aic %p)",
@@ -3068,6 +3066,7 @@ static int scst_ioc_keeper_thread(void *arg)
 	put_io_context(aic_keeper->aic);
 
 	/* We are ready */
+	aic_keeper->aic_ready = true;
 	wake_up_all(&aic_keeper->aic_keeper_waitQ);
 
 	wait_event_interruptible(aic_keeper->aic_keeper_waitQ,
@@ -3129,7 +3128,7 @@ int scst_tgt_dev_setup_threads(struct scst_tgt_dev *tgt_dev)
 			}
 
 			wait_event(aic_keeper->aic_keeper_waitQ,
-				aic_keeper->aic != NULL);
+				aic_keeper->aic_ready);
 
 			TRACE_MGMT_DBG("Created async io context %p "
 				"for not shared tgt_dev %p (dev %s)",

scst/src/scst_main.c

@@ -1525,7 +1525,7 @@ out_wait:
 		 * Wait for io_context gets initialized to avoid possible races
 		 * for it from the sharing it tgt_devs.
 		 */
-		while ((volatile bool)!cmd_threads->io_context_ready) {
+		while (!*(volatile bool*)&cmd_threads->io_context_ready) {
 			TRACE_DBG("Waiting for io_context for cmd_threads %p "
 				"initialized", cmd_threads);
 			msleep(50);

scst/src/scst_priv.h

@@ -199,6 +199,10 @@ static inline bool scst_set_io_context(struct scst_cmd *cmd,
 {
 	bool res;
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 25)
+	return false;
+#endif
+
 #ifdef CONFIG_SCST_TEST_IO_IN_SIRQ
 	return false;
 #endif

scst/src/scst_sysfs.c

@@ -2339,7 +2339,7 @@ int scst_sess_sysfs_create(struct scst_session *sess)
 
 restart:
 	list_for_each_entry(s, &sess->tgt->sess_list, sess_list_entry) {
-		if (!sess->sess_kobj_ready)
+		if (!s->sess_kobj_ready)
 			continue;
 
 		if (strcmp(name, kobject_name(&s->sess_kobj)) == 0) {
@@ -2368,6 +2368,8 @@ restart:
 
 	init_completion(&sess->sess_kobj_release_cmpl);
 
+	TRACE_DBG("Adding session %s to sysfs", name);
+
 	res = kobject_init_and_add(&sess->sess_kobj, &scst_session_ktype,
 			      sess->tgt->tgt_sess_kobj, name);
 	if (res != 0) {
@@ -2410,7 +2412,8 @@ void scst_sess_sysfs_del(struct scst_session *sess)
 	if (!sess->sess_kobj_ready)
 		goto out;
 
-	TRACE_DBG("Deleting session %s", kobject_name(&sess->sess_kobj));
+	TRACE_DBG("Deleting session %s from sysfs",
+		kobject_name(&sess->sess_kobj));
 
 	kobject_del(&sess->sess_kobj);
 	kobject_put(&sess->sess_kobj);

scst/src/scst_targ.c

@@ -4252,13 +4252,6 @@ static inline int test_cmd_threads(struct scst_cmd_threads *p_cmd_threads)
 	return res;
 }
 
-#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 25)
-static void scst_io_context_kref_release(struct kref *kref)
-{
-	/* Nothing to do */
-}
-#endif
-
 int scst_cmd_thread(void *arg)
 {
 	struct scst_cmd_threads *p_cmd_threads = (struct scst_cmd_threads *)arg;
@@ -4280,9 +4273,7 @@ int scst_cmd_thread(void *arg)
 
 	if (p_cmd_threads != &scst_main_cmd_threads) {
 		if (p_cmd_threads->io_context == NULL) {
-#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 19)
-			p_cmd_threads->io_context = get_io_context(GFP_KERNEL);
-#else
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 25)
 			p_cmd_threads->io_context = get_io_context(GFP_KERNEL, -1);
 #endif
 			TRACE_MGMT_DBG("Alloced new IO context %p "
@@ -4294,18 +4285,10 @@ int scst_cmd_thread(void *arg)
 			 * ref counted via nr_threads below.
 			 */
 			put_io_context(p_cmd_threads->io_context);
-#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 25)
-			kref_init(&p_cmd_threads->io_context_kref);
-#endif
 		} else {
-			put_io_context(current->io_context);
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 25)
+			put_io_context(current->io_context);
 			current->io_context = ioc_task_link(p_cmd_threads->io_context);
-#else
-			current->io_context = p_cmd_threads->io_context;
-			kref_get(&p_cmd_threads->io_context_kref);
-			TRACE_DBG("new refcount %d",
-				atomic_read(&p_cmd_threads->io_context_kref.refcount));
 #endif
 			TRACE_MGMT_DBG("Linked IO context %p "
 				"(p_cmd_threads %p)", p_cmd_threads->io_context,
@@ -4353,18 +4336,6 @@ int scst_cmd_thread(void *arg)
 		 !list_empty(&p_cmd_threads->active_cmd_list));
 
 	if (p_cmd_threads != &scst_main_cmd_threads) {
-#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 25)
-		TRACE_DBG("old refcount %d",
-			atomic_read(&p_cmd_threads->io_context_kref.refcount));
-		if (!kref_put(&p_cmd_threads->io_context_kref,
-				scst_io_context_kref_release)) {
-			/*
-			 * Prevent io_context from being destroyed, we still
-			 * need it.
-			 */
-			current->io_context = NULL;
-		}
-#endif
 		if (p_cmd_threads->nr_threads == 1)
 			p_cmd_threads->io_context = NULL;
 	}