rcutorture: Abstract torture_create_kthread()

Creation of kthreads is not RCU-specific, so this commit abstracts
out torture_create_kthread(), saving a few tens of lines of code in
the process.

This change requires modifying VERBOSE_TOROUT_ERRSTRING() to take a
non-const string, so that _torture_create_kthread() can avoid an
open-coded substitute.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

include/linux/torture.h

@@ -47,7 +47,7 @@
 #define VERBOSE_TOROUT_STRING(s) \
 	do { if (verbose) pr_alert("%s" TORTURE_FLAG " %s\n", torture_type, s); } while (0)
 #define VERBOSE_TOROUT_ERRSTRING(s) \
-	do { if (verbose) pr_alert("%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
+	do { if (verbose) pr_alert("%s" TORTURE_FLAG "!!! %s\n", torture_type, s); } while (0)
 
 /* Definitions for a non-string torture-test module parameter. */
 #define torture_parm(type, name, init, msg) \
@@ -89,5 +89,11 @@ bool torture_cleanup(void);
 bool torture_must_stop(void);
 bool torture_must_stop_irq(void);
 void torture_kthread_stopping(char *title);
+int _torture_create_kthread(int (*fn)(void *arg), void *arg, char *s, char *m,
+			     char *f, struct task_struct **tp);
+
+#define torture_create_kthread(n, arg, tp) \
+	_torture_create_kthread(n, (arg), #n, "Creating " #n " task", \
+				"Failed to create " #n, &(tp))
 
 #endif /* __LINUX_TORTURE_H */

kernel/rcu/rcutorture.c

@@ -1105,19 +1105,9 @@ static int rcu_torture_stall(void *args)
 /* Spawn CPU-stall kthread, if stall_cpu specified. */
 static int __init rcu_torture_stall_init(void)
 {
-	int ret;
-
 	if (stall_cpu <= 0)
 		return 0;
-	VERBOSE_TOROUT_STRING("Creating rcu_torture_stall task");
-	stall_task = kthread_run(rcu_torture_stall, NULL, "rcu_torture_stall");
-	if (IS_ERR(stall_task)) {
-		ret = PTR_ERR(stall_task);
-		stall_task = NULL;
-		return ret;
-	}
-	torture_shuffle_task_register(stall_task);
-	return 0;
+	return torture_create_kthread(rcu_torture_stall, NULL, stall_task);
 }
 
 /* Clean up after the CPU-stall kthread, if one was spawned. */
@@ -1226,29 +1216,13 @@ static int rcu_torture_barrier_init(void)
 		return -ENOMEM;
 	for (i = 0; i < n_barrier_cbs; i++) {
 		init_waitqueue_head(&barrier_cbs_wq[i]);
-		VERBOSE_TOROUT_STRING("Creating rcu_torture_barrier_cbs task");
-		barrier_cbs_tasks[i] = kthread_run(rcu_torture_barrier_cbs,
-						   (void *)(long)i,
-						   "rcu_torture_barrier_cbs");
-		if (IS_ERR(barrier_cbs_tasks[i])) {
-			ret = PTR_ERR(barrier_cbs_tasks[i]);
-			VERBOSE_TOROUT_ERRSTRING("Failed to create rcu_torture_barrier_cbs");
-			barrier_cbs_tasks[i] = NULL;
+		ret = torture_create_kthread(rcu_torture_barrier_cbs,
+					     (void *)(long)i,
+					     barrier_cbs_tasks[i]);
+		if (ret)
 			return ret;
-		}
-		torture_shuffle_task_register(barrier_cbs_tasks[i]);
 	}
-	VERBOSE_TOROUT_STRING("Creating rcu_torture_barrier task");
-	barrier_task = kthread_run(rcu_torture_barrier, NULL,
-				   "rcu_torture_barrier");
-	if (IS_ERR(barrier_task)) {
-		ret = PTR_ERR(barrier_task);
-		VERBOSE_TOROUT_ERRSTRING("Failed to create rcu_torture_barrier");
-		barrier_task = NULL;
-		return ret;
-	}
-	torture_shuffle_task_register(barrier_task);
-	return 0;
+	return torture_create_kthread(rcu_torture_barrier, NULL, barrier_task);
 }
 
 /* Clean up after RCU barrier testing. */
@@ -1516,17 +1490,10 @@ rcu_torture_init(void)
 
 	/* Start up the kthreads. */
 
-	VERBOSE_TOROUT_STRING("Creating rcu_torture_writer task");
-	writer_task = kthread_create(rcu_torture_writer, NULL,
-				     "rcu_torture_writer");
-	if (IS_ERR(writer_task)) {
-		firsterr = PTR_ERR(writer_task);
-		VERBOSE_TOROUT_ERRSTRING("Failed to create writer");
-		writer_task = NULL;
+	firsterr = torture_create_kthread(rcu_torture_writer, NULL,
+					  writer_task);
+	if (firsterr)
 		goto unwind;
-	}
-	torture_shuffle_task_register(writer_task);
-	wake_up_process(writer_task);
 	fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
 				   GFP_KERNEL);
 	if (fakewriter_tasks == NULL) {
@@ -1535,16 +1502,10 @@ rcu_torture_init(void)
 		goto unwind;
 	}
 	for (i = 0; i < nfakewriters; i++) {
-		VERBOSE_TOROUT_STRING("Creating rcu_torture_fakewriter task");
-		fakewriter_tasks[i] = kthread_run(rcu_torture_fakewriter, NULL,
-						  "rcu_torture_fakewriter");
-		if (IS_ERR(fakewriter_tasks[i])) {
-			firsterr = PTR_ERR(fakewriter_tasks[i]);
-			VERBOSE_TOROUT_ERRSTRING("Failed to create fakewriter");
-			fakewriter_tasks[i] = NULL;
+		firsterr = torture_create_kthread(rcu_torture_fakewriter,
+						  NULL, fakewriter_tasks[i]);
+		if (firsterr)
 			goto unwind;
-		}
-		torture_shuffle_task_register(fakewriter_tasks[i]);
 	}
 	reader_tasks = kzalloc(nrealreaders * sizeof(reader_tasks[0]),
 			       GFP_KERNEL);
@@ -1554,28 +1515,16 @@ rcu_torture_init(void)
 		goto unwind;
 	}
 	for (i = 0; i < nrealreaders; i++) {
-		VERBOSE_TOROUT_STRING("Creating rcu_torture_reader task");
-		reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
-					      "rcu_torture_reader");
-		if (IS_ERR(reader_tasks[i])) {
-			firsterr = PTR_ERR(reader_tasks[i]);
-			VERBOSE_TOROUT_ERRSTRING("Failed to create reader");
-			reader_tasks[i] = NULL;
+		firsterr = torture_create_kthread(rcu_torture_reader, NULL,
+						  reader_tasks[i]);
+		if (firsterr)
 			goto unwind;
-		}
-		torture_shuffle_task_register(reader_tasks[i]);
 	}
 	if (stat_interval > 0) {
-		VERBOSE_TOROUT_STRING("Creating rcu_torture_stats task");
-		stats_task = kthread_run(rcu_torture_stats, NULL,
-					"rcu_torture_stats");
-		if (IS_ERR(stats_task)) {
-			firsterr = PTR_ERR(stats_task);
-			VERBOSE_TOROUT_ERRSTRING("Failed to create stats");
-			stats_task = NULL;
+		firsterr = torture_create_kthread(rcu_torture_stats, NULL,
+						  stats_task);
+		if (firsterr)
 			goto unwind;
-		}
-		torture_shuffle_task_register(stats_task);
 	}
 	if (test_no_idle_hz) {
 		firsterr = torture_shuffle_init(shuffle_interval * HZ);
@@ -1593,16 +1542,9 @@ rcu_torture_init(void)
 		fqs_duration = 0;
 	if (fqs_duration) {
 		/* Create the fqs thread */
-		VERBOSE_TOROUT_STRING("Creating rcu_torture_fqs task");
-		fqs_task = kthread_run(rcu_torture_fqs, NULL,
-				       "rcu_torture_fqs");
-		if (IS_ERR(fqs_task)) {
-			firsterr = PTR_ERR(fqs_task);
-			VERBOSE_TOROUT_ERRSTRING("Failed to create fqs");
-			fqs_task = NULL;
+		torture_create_kthread(rcu_torture_fqs, NULL, fqs_task);
+		if (firsterr)
 			goto unwind;
-		}
-		torture_shuffle_task_register(fqs_task);
 	}
 	if (test_boost_interval < 1)
 		test_boost_interval = 1;

kernel/torture.c

@@ -180,23 +180,16 @@ torture_onoff(void *arg)
  */
 int torture_onoff_init(long ooholdoff, long oointerval)
 {
-#ifdef CONFIG_HOTPLUG_CPU
-	int ret;
+	int ret = 0;
 
+#ifdef CONFIG_HOTPLUG_CPU
 	onoff_holdoff = ooholdoff;
 	onoff_interval = oointerval;
 	if (onoff_interval <= 0)
 		return 0;
-	VERBOSE_TOROUT_STRING("Creating torture_onoff task");
-	onoff_task = kthread_run(torture_onoff, NULL, "torture_onoff");
-	if (IS_ERR(onoff_task)) {
-		ret = PTR_ERR(onoff_task);
-		onoff_task = NULL;
-		return ret;
-	}
-	torture_shuffle_task_register(onoff_task);
+	ret = torture_create_kthread(torture_onoff, NULL, onoff_task);
 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(torture_onoff_init);
 
@@ -379,8 +372,6 @@ static int torture_shuffle(void *arg)
  */
 int torture_shuffle_init(long shuffint)
 {
-	int ret;
-
 	shuffle_interval = shuffint;
 
 	shuffle_idle_cpu = -1;
@@ -391,17 +382,7 @@ int torture_shuffle_init(long shuffint)
 	}
 
 	/* Create the shuffler thread */
-	VERBOSE_TOROUT_STRING("Creating torture_shuffle task");
-	shuffler_task = kthread_run(torture_shuffle, NULL, "torture_shuffle");
-	if (IS_ERR(shuffler_task)) {
-		ret = PTR_ERR(shuffler_task);
-		free_cpumask_var(shuffle_tmp_mask);
-		VERBOSE_TOROUT_ERRSTRING("Failed to create shuffler");
-		shuffler_task = NULL;
-		return ret;
-	}
-	torture_shuffle_task_register(shuffler_task);
-	return 0;
+	return torture_create_kthread(torture_shuffle, NULL, shuffler_task);
 }
 EXPORT_SYMBOL_GPL(torture_shuffle_init);
 
@@ -483,25 +464,16 @@ static int torture_shutdown(void *arg)
  */
 int torture_shutdown_init(int ssecs, void (*cleanup)(void))
 {
-	int ret;
+	int ret = 0;
 
 	shutdown_secs = ssecs;
 	torture_shutdown_hook = cleanup;
 	if (shutdown_secs > 0) {
-		VERBOSE_TOROUT_STRING("Creating torture_shutdown task");
 		shutdown_time = jiffies + shutdown_secs * HZ;
-		shutdown_task = kthread_create(torture_shutdown, NULL,
-					       "torture_shutdown");
-		if (IS_ERR(shutdown_task)) {
-			ret = PTR_ERR(shutdown_task);
-			VERBOSE_TOROUT_ERRSTRING("Failed to create shutdown");
-			shutdown_task = NULL;
-			return ret;
-		}
-		torture_shuffle_task_register(shutdown_task);
-		wake_up_process(shutdown_task);
+		ret = torture_create_kthread(torture_shutdown, NULL,
+					     shutdown_task);
 	}
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(torture_shutdown_init);
 
@@ -595,16 +567,8 @@ int torture_stutter_init(int s)
 	int ret;
 
 	stutter = s;
-	VERBOSE_TOROUT_STRING("Creating torture_stutter task");
-	stutter_task = kthread_run(torture_stutter, NULL, "torture_stutter");
-	if (IS_ERR(stutter_task)) {
-		ret = PTR_ERR(stutter_task);
-		VERBOSE_TOROUT_ERRSTRING("Failed to create stutter");
-		stutter_task = NULL;
-		return ret;
-	}
-	torture_shuffle_task_register(stutter_task);
-	return 0;
+	ret = torture_create_kthread(torture_stutter, NULL, stutter_task);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(torture_stutter_init);
 
@@ -714,3 +678,25 @@ void torture_kthread_stopping(char *title)
 	}
 }
 EXPORT_SYMBOL_GPL(torture_kthread_stopping);
+
+/*
+ * Create a generic torture kthread that is immediately runnable.  If you
+ * need the kthread to be stopped so that you can do something to it before
+ * it starts, you will need to open-code your own.
+ */
+int _torture_create_kthread(int (*fn)(void *arg), void *arg, char *s, char *m,
+			    char *f, struct task_struct **tp)
+{
+	int ret = 0;
+
+	VERBOSE_TOROUT_STRING(m);
+	*tp = kthread_run(fn, arg, s);
+	if (IS_ERR(*tp)) {
+		ret = PTR_ERR(*tp);
+		VERBOSE_TOROUT_ERRSTRING(f);
+		*tp = NULL;
+	}
+	torture_shuffle_task_register(*tp);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(_torture_create_kthread);