3 files changed, 104 insertions, 59 deletions

diff --git a/include/linux/torture.h b/include/linux/torture.h
index 0259db38bfb0..203f127d9ddf 100644
--- a/include/linux/torture.h
+++ b/include/linux/torture.h
@@ -75,8 +75,13 @@ int torture_shuffle_init(long shuffint);
 /* Shutdown task absorption, for when the tasks cannot safely be killed. */
 void torture_shutdown_absorb(const char *title);
 
+/* Task stuttering, which forces load/no-load transitions. */
+void stutter_wait(const char *title);
+int torture_stutter_init(int s);
+void torture_stutter_cleanup(void);
+
 /* Initialization and cleanup. */
-void torture_init_begin(char *ttype, bool v);
+void torture_init_begin(char *ttype, bool v, int *runnable);
 void torture_init_end(void);
 bool torture_cleanup(void);
 bool torture_must_stop(void);
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 9357c88cc8cc..4329ad14f8dc 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -103,7 +103,6 @@ static struct task_struct *writer_task;
 static struct task_struct **fakewriter_tasks;
 static struct task_struct **reader_tasks;
 static struct task_struct *stats_task;
-static struct task_struct *stutter_task;
 static struct task_struct *fqs_task;
 static struct task_struct *boost_tasks[NR_CPUS];
 static struct task_struct *shutdown_task;
@@ -145,8 +144,6 @@ static long n_barrier_attempts;
 static long n_barrier_successes;
 static struct list_head rcu_torture_removed;
 
-static int stutter_pause_test;
-
 #if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE)
 #define RCUTORTURE_RUNNABLE_INIT 1
 #else
@@ -222,18 +219,6 @@ rcu_torture_free(struct rcu_torture *p)
         spin_unlock_bh(&rcu_torture_lock);
 }
 
-static void
-rcu_stutter_wait(const char *title)
-{
-        while (stutter_pause_test || !rcutorture_runnable) {
-                if (rcutorture_runnable)
-                        schedule_timeout_interruptible(1);
-                else
-                        schedule_timeout_interruptible(round_jiffies_relative(HZ));
-                torture_shutdown_absorb(title);
-        }
-}
-
 /*
  * Operations vector for selecting different types of tests.
  */
@@ -571,7 +556,7 @@ static int rcu_torture_boost(void *arg)
                 oldstarttime = boost_starttime;
                 while (ULONG_CMP_LT(jiffies, oldstarttime)) {
                         schedule_timeout_interruptible(oldstarttime - jiffies);
-                        rcu_stutter_wait("rcu_torture_boost");
+                        stutter_wait("rcu_torture_boost");
                         if (torture_must_stop())
                                 goto checkwait;
                 }
@@ -593,7 +578,7 @@ static int rcu_torture_boost(void *arg)
                                 call_rcu_time = jiffies;
                         }
                         cond_resched();
-                        rcu_stutter_wait("rcu_torture_boost");
+                        stutter_wait("rcu_torture_boost");
                         if (torture_must_stop())
                                 goto checkwait;
                 }
@@ -618,7 +603,7 @@ static int rcu_torture_boost(void *arg)
                 }
 
                 /* Go do the stutter. */
-checkwait:      rcu_stutter_wait("rcu_torture_boost");
+checkwait:      stutter_wait("rcu_torture_boost");
         } while (!torture_must_stop());
 
         /* Clean up and exit. */
@@ -656,7 +641,7 @@ rcu_torture_fqs(void *arg)
                         udelay(fqs_holdoff);
                         fqs_burst_remaining -= fqs_holdoff;
                 }
-                rcu_stutter_wait("rcu_torture_fqs");
+                stutter_wait("rcu_torture_fqs");
         } while (!torture_must_stop());
         VERBOSE_TOROUT_STRING("rcu_torture_fqs task stopping");
         torture_shutdown_absorb("rcu_torture_fqs");
@@ -728,7 +713,7 @@ rcu_torture_writer(void *arg)
                         }
                 }
                 rcutorture_record_progress(++rcu_torture_current_version);
-                rcu_stutter_wait("rcu_torture_writer");
+                stutter_wait("rcu_torture_writer");
         } while (!torture_must_stop());
         VERBOSE_TOROUT_STRING("rcu_torture_writer task stopping");
         torture_shutdown_absorb("rcu_torture_writer");
@@ -765,7 +750,7 @@ rcu_torture_fakewriter(void *arg)
                 } else {
                         cur_ops->exp_sync();
                 }
-                rcu_stutter_wait("rcu_torture_fakewriter");
+                stutter_wait("rcu_torture_fakewriter");
         } while (!torture_must_stop());
 
         VERBOSE_TOROUT_STRING("rcu_torture_fakewriter task stopping");
@@ -910,7 +895,7 @@ rcu_torture_reader(void *arg)
                 preempt_enable();
                 cur_ops->readunlock(idx);
                 schedule();
-                rcu_stutter_wait("rcu_torture_reader");
+                stutter_wait("rcu_torture_reader");
         } while (!torture_must_stop());
         VERBOSE_TOROUT_STRING("rcu_torture_reader task stopping");
         torture_shutdown_absorb("rcu_torture_reader");
@@ -1034,25 +1019,6 @@ rcu_torture_stats(void *arg)
         return 0;
 }
 
-/* Cause the rcutorture test to "stutter", starting and stopping all
- * threads periodically.
- */
-static int
-rcu_torture_stutter(void *arg)
-{
-        VERBOSE_TOROUT_STRING("rcu_torture_stutter task started");
-        do {
-                schedule_timeout_interruptible(stutter * HZ);
-                stutter_pause_test = 1;
-                if (!kthread_should_stop())
-                        schedule_timeout_interruptible(stutter * HZ);
-                stutter_pause_test = 0;
-                torture_shutdown_absorb("rcu_torture_stutter");
-        } while (!kthread_should_stop());
-        VERBOSE_TOROUT_STRING("rcu_torture_stutter task stopping");
-        return 0;
-}
-
 static inline void
 rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
 {
@@ -1403,11 +1369,7 @@ rcu_torture_cleanup(void)
 
         rcu_torture_barrier_cleanup();
         rcu_torture_stall_cleanup();
-        if (stutter_task) {
-                VERBOSE_TOROUT_STRING("Stopping rcu_torture_stutter task");
-                kthread_stop(stutter_task);
-        }
-        stutter_task = NULL;
+        torture_stutter_cleanup();
 
         if (writer_task) {
                 VERBOSE_TOROUT_STRING("Stopping rcu_torture_writer task");
@@ -1548,7 +1510,7 @@ rcu_torture_init(void)
                 &rcu_ops, &rcu_bh_ops, &srcu_ops, &sched_ops,
         };
 
-        torture_init_begin(torture_type, verbose);
+        torture_init_begin(torture_type, verbose, &rcutorture_runnable);
 
         /* Process args and tell the world that the torturer is on the job. */
         for (i = 0; i < ARRAY_SIZE(torture_ops); i++) {
@@ -1682,21 +1644,14 @@ rcu_torture_init(void)
         if (stutter < 0)
                 stutter = 0;
         if (stutter) {
-                /* Create the stutter thread */
-                stutter_task = kthread_run(rcu_torture_stutter, NULL,
-                                          "rcu_torture_stutter");
-                if (IS_ERR(stutter_task)) {
-                        firsterr = PTR_ERR(stutter_task);
-                        VERBOSE_TOROUT_ERRSTRING("Failed to create stutter");
-                        stutter_task = NULL;
+                firsterr = torture_stutter_init(stutter * HZ);
+                if (firsterr)
                         goto unwind;
-                }
-                torture_shuffle_task_register(stutter_task);
         }
         if (fqs_duration < 0)
                 fqs_duration = 0;
         if (fqs_duration) {
-                /* Create the stutter thread */
+                /* Create the fqs thread */
                 fqs_task = kthread_run(rcu_torture_fqs, NULL,
                                        "rcu_torture_fqs");
                 if (IS_ERR(fqs_task)) {
diff --git a/kernel/torture.c b/kernel/torture.c
index d51de3029a5c..b30c2ee78580 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -58,6 +58,7 @@ static bool verbose;
 #define FULLSTOP_RMMOD    2     /* Normal rmmod of torture. */
 static int fullstop = FULLSTOP_RMMOD;
 static DEFINE_MUTEX(fullstop_mutex);
+static int *torture_runnable;
 
 #ifdef CONFIG_HOTPLUG_CPU
 
@@ -453,16 +454,100 @@ static struct notifier_block torture_shutdown_nb = {
 };
 
 /*
+ * Variables for stuttering, which means to periodically pause and
+ * restart testing in order to catch bugs that appear when load is
+ * suddenly applied to or removed from the system.
+ */
+static struct task_struct *stutter_task;
+static int stutter_pause_test;
+static int stutter;
+
+/*
+ * Block until the stutter interval ends.  This must be called periodically
+ * by all running kthreads that need to be subject to stuttering.
+ */
+void stutter_wait(const char *title)
+{
+        while (ACCESS_ONCE(stutter_pause_test) ||
+               (torture_runnable && !ACCESS_ONCE(*torture_runnable))) {
+                if (stutter_pause_test)
+                        schedule_timeout_interruptible(1);
+                else
+                        schedule_timeout_interruptible(round_jiffies_relative(HZ));
+                torture_shutdown_absorb(title);
+        }
+}
+EXPORT_SYMBOL_GPL(stutter_wait);
+
+/*
+ * Cause the torture test to "stutter", starting and stopping all
+ * threads periodically.
+ */
+static int torture_stutter(void *arg)
+{
+        VERBOSE_TOROUT_STRING("torture_stutter task started");
+        do {
+                if (!torture_must_stop()) {
+                        schedule_timeout_interruptible(stutter);
+                        ACCESS_ONCE(stutter_pause_test) = 1;
+                }
+                if (!torture_must_stop())
+                        schedule_timeout_interruptible(stutter);
+                ACCESS_ONCE(stutter_pause_test) = 0;
+                torture_shutdown_absorb("torture_stutter");
+        } while (!torture_must_stop());
+        VERBOSE_TOROUT_STRING("torture_stutter task stopping");
+        return 0;
+}
+
+/*
+ * Initialize and kick off the torture_stutter kthread.
+ */
+int torture_stutter_init(int s)
+{
+        int ret;
+
+        stutter = s;
+        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;
+}
+EXPORT_SYMBOL_GPL(torture_stutter_init);
+
+/*
+ * Cleanup after the torture_stutter kthread.
+ */
+void torture_stutter_cleanup(void)
+{
+        if (!stutter_task)
+                return;
+        VERBOSE_TOROUT_STRING("Stopping torture_stutter task");
+        kthread_stop(stutter_task);
+        stutter_task = NULL;
+}
+EXPORT_SYMBOL_GPL(torture_stutter_cleanup);
+
+/*
  * Initialize torture module.  Please note that this is -not- invoked via
  * the usual module_init() mechanism, but rather by an explicit call from
  * the client torture module.  This call must be paired with a later
  * torture_init_end().
+ *
+ * The runnable parameter points to a flag that controls whether or not
+ * the test is currently runnable.  If there is no such flag, pass in NULL.
  */
-void __init torture_init_begin(char *ttype, bool v)
+void __init torture_init_begin(char *ttype, bool v, int *runnable)
 {
         mutex_lock(&fullstop_mutex);
         torture_type = ttype;
         verbose = v;
+        torture_runnable = runnable;
         fullstop = FULLSTOP_DONTSTOP;
 
 }