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>

3 files changed, 60 insertions, 126 deletions

diff --git a/include/linux/torture.h b/include/linux/torture.h
index 2ea11094daf6..430cc3008628 100644
--- a/include/linux/torture.h
+++ b/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 */
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 25e9b16fe7f0..a6f6c8418d87 100644
--- a/kernel/rcu/rcutorture.c
+++ b/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;
diff --git a/kernel/torture.c b/kernel/torture.c
index 330576660cf4..439451821a7f 100644
--- a/kernel/torture.c
+++ b/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);