rcu-tasks: Add RCU tasks to rcutorture writer stall output

This commit adds state for each RCU-tasks flavor to the rcutorture
writer stall output.  The initial state is minimal, but you have to
start somewhere.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
[ paulmck: Fixes based on feedback from kbuild test robot. ]

kernel/rcu/rcu.h

@@ -431,6 +431,7 @@ bool rcu_gp_is_expedited(void);  /* Internal RCU use. */
 void rcu_expedite_gp(void);
 void rcu_unexpedite_gp(void);
 void rcupdate_announce_bootup_oddness(void);
+void show_rcu_tasks_gp_kthreads(void);
 void rcu_request_urgent_qs_task(struct task_struct *t);
 #endif /* #else #ifdef CONFIG_TINY_RCU */
 

kernel/rcu/tasks.h

@@ -219,6 +219,16 @@ static void __init rcu_tasks_bootup_oddness(void)
 
 #endif /* #ifndef CONFIG_TINY_RCU */
 
+/* Dump out rcutorture-relevant state common to all RCU-tasks flavors. */
+static void show_rcu_tasks_generic_gp_kthread(struct rcu_tasks *rtp, char *s)
+{
+	pr_info("%s %c%c %s\n",
+		rtp->kname,
+		".k"[!!data_race(rtp->kthread_ptr)],
+		".C"[!!data_race(rtp->cbs_head)],
+		s);
+}
+
 #ifdef CONFIG_TASKS_RCU
 
 ////////////////////////////////////////////////////////////////////////
@@ -482,7 +492,14 @@ static int __init rcu_spawn_tasks_kthread(void)
 }
 core_initcall(rcu_spawn_tasks_kthread);
 
-#endif /* #ifdef CONFIG_TASKS_RCU */
+static void show_rcu_tasks_classic_gp_kthread(void)
+{
+	show_rcu_tasks_generic_gp_kthread(&rcu_tasks, "");
+}
+
+#else /* #ifdef CONFIG_TASKS_RCU */
+static void show_rcu_tasks_classic_gp_kthread(void) { }
+#endif /* #else #ifdef CONFIG_TASKS_RCU */
 
 #ifdef CONFIG_TASKS_RUDE_RCU
 
@@ -578,7 +595,14 @@ static int __init rcu_spawn_tasks_rude_kthread(void)
 }
 core_initcall(rcu_spawn_tasks_rude_kthread);
 
-#endif /* #ifdef CONFIG_TASKS_RUDE_RCU */
+static void show_rcu_tasks_rude_gp_kthread(void)
+{
+	show_rcu_tasks_generic_gp_kthread(&rcu_tasks_rude, "");
+}
+
+#else /* #ifdef CONFIG_TASKS_RUDE_RCU */
+static void show_rcu_tasks_rude_gp_kthread(void) {}
+#endif /* #else #ifdef CONFIG_TASKS_RUDE_RCU */
 
 ////////////////////////////////////////////////////////////////////////
 //
@@ -982,10 +1006,27 @@ static int __init rcu_spawn_tasks_trace_kthread(void)
 }
 core_initcall(rcu_spawn_tasks_trace_kthread);
 
+static void show_rcu_tasks_trace_gp_kthread(void)
+{
+	char buf[32];
+
+	sprintf(buf, "N%d", atomic_read(&trc_n_readers_need_end));
+	show_rcu_tasks_generic_gp_kthread(&rcu_tasks_trace, buf);
+}
+
 #else /* #ifdef CONFIG_TASKS_TRACE_RCU */
 void exit_tasks_rcu_finish_trace(struct task_struct *t) { }
+static inline void show_rcu_tasks_trace_gp_kthread(void) {}
 #endif /* #else #ifdef CONFIG_TASKS_TRACE_RCU */
 
+void show_rcu_tasks_gp_kthreads(void)
+{
+	show_rcu_tasks_classic_gp_kthread();
+	show_rcu_tasks_rude_gp_kthread();
+	show_rcu_tasks_trace_gp_kthread();
+}
+
 #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
 static inline void rcu_tasks_bootup_oddness(void) {}
+void show_rcu_tasks_gp_kthreads(void) {}
 #endif /* #else #ifdef CONFIG_TASKS_RCU_GENERIC */

kernel/rcu/tree_stall.h

@@ -649,7 +649,7 @@ void show_rcu_gp_kthreads(void)
 		if (rcu_segcblist_is_offloaded(&rdp->cblist))
 			show_rcu_nocb_state(rdp);
 	}
-	/* sched_show_task(rcu_state.gp_kthread); */
+	show_rcu_tasks_gp_kthreads();
 }
 EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads);