rcutorture: Export RCU grace-period kthread wait state to rcutorture

This commit allows rcutorture to print additional state for the RCU grace-period kthreads in cases where RCU seems reluctant to start a new grace period. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>

rcutorture: Export RCU grace-period kthread wait state to rcutorture
This commit allows rcutorture to print additional state for the RCU grace-period kthreads in cases where RCU seems reluctant to start a new grace period. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Paul E. McKenney
1 parent 945fa9c631
Showing 5 changed files with 30 additions and 1 deletions Side-by-side Diff
include/linux/rcutiny.h
include/linux/rcutree.h
kernel/rcu/rcutorture.c
kernel/rcu/tree.c
kernel/rcu/tree.h
@@ -119,6 +119,10 @@
 {
 }
  
+static inline void show_rcu_gp_kthreads(void)
+{
+}
+
 static inline void rcu_cpu_stall_reset(void)
 {
 }
@@ -84,6 +84,7 @@
 long rcu_batches_completed(void);
 long rcu_batches_completed_bh(void);
 long rcu_batches_completed_sched(void);
+void show_rcu_gp_kthreads(void);
  
 void rcu_force_quiescent_state(void);
 void rcu_bh_force_quiescent_state(void);
@@ -1034,6 +1034,7 @@
 				"??? Writer stall state %d g%lu c%lu f%#x\n",
 				rcu_torture_writer_state,
 				gpnum, completed, flags);
+		show_rcu_gp_kthreads();
 		rcutorture_trace_dump();
 	}
 	rtcv_snap = rcu_torture_current_version;
@@ -280,6 +280,21 @@
 EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
  
 /*
+ * Show the state of the grace-period kthreads.
+ */
+void show_rcu_gp_kthreads(void)
+{
+	struct rcu_state *rsp;
+
+	for_each_rcu_flavor(rsp) {
+		pr_info("%s: wait state: %d ->state: %#lx\n",
+			rsp->name, rsp->gp_state, rsp->gp_kthread->state);
+		/* sched_show_task(rsp->gp_kthread); */
+	}
+}
+EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads);
+
+/*
  * Record the number of times rcutorture tests have been initiated and
  * terminated.  This information allows the debugfs tracing stats to be
  * correlated to the rcutorture messages, even when the rcutorture module
@@ -1626,6 +1641,7 @@
 			trace_rcu_grace_period(rsp->name,
 					       ACCESS_ONCE(rsp->gpnum),
 					       TPS("reqwait"));
+			rsp->gp_state = RCU_GP_WAIT_GPS;
 			wait_event_interruptible(rsp->gp_wq,
 						 ACCESS_ONCE(rsp->gp_flags) &
 						 RCU_GP_FLAG_INIT);
@@ -1653,6 +1669,7 @@
 			trace_rcu_grace_period(rsp->name,
 					       ACCESS_ONCE(rsp->gpnum),
 					       TPS("fqswait"));
+			rsp->gp_state = RCU_GP_WAIT_FQS;
 			ret = wait_event_interruptible_timeout(rsp->gp_wq,
 					((gf = ACCESS_ONCE(rsp->gp_flags)) &
 					 RCU_GP_FLAG_FQS) ||
@@ -406,7 +406,8 @@
 	unsigned long completed;		/* # of last completed gp. */
 	struct task_struct *gp_kthread;		/* Task for grace periods. */
 	wait_queue_head_t gp_wq;		/* Where GP task waits. */
-	int gp_flags;				/* Commands for GP task. */
+	short gp_flags;				/* Commands for GP task. */
+	short gp_state;				/* GP kthread sleep state. */
  
 	/* End of fields guarded by root rcu_node's lock. */
  
@@ -468,6 +469,11 @@
 /* Values for rcu_state structure's gp_flags field. */
 #define RCU_GP_FLAG_INIT 0x1	/* Need grace-period initialization. */
 #define RCU_GP_FLAG_FQS  0x2	/* Need grace-period quiescent-state forcing. */
+
+/* Values for rcu_state structure's gp_flags field. */
+#define RCU_GP_WAIT_INIT 0	/* Initial state. */
+#define RCU_GP_WAIT_GPS  1	/* Wait for grace-period start. */
+#define RCU_GP_WAIT_FQS  2	/* Wait for force-quiescent-state time. */
  
 extern struct list_head rcu_struct_flavors;
...	...	@@ -119,6 +119,10 @@
119	119	{
120	120	}
121	121
	122	+static inline void show_rcu_gp_kthreads(void)
	123	+{
	124	+}
	125	+
122	126	static inline void rcu_cpu_stall_reset(void)
123	127	{
124	128	}
...	...	@@ -84,6 +84,7 @@
84	84	long rcu_batches_completed(void);
85	85	long rcu_batches_completed_bh(void);
86	86	long rcu_batches_completed_sched(void);
	87	+void show_rcu_gp_kthreads(void);
87	88
88	89	void rcu_force_quiescent_state(void);
89	90	void rcu_bh_force_quiescent_state(void);
...	...	@@ -1034,6 +1034,7 @@
1034	1034	"??? Writer stall state %d g%lu c%lu f%#x\n",
1035	1035	rcu_torture_writer_state,
1036	1036	gpnum, completed, flags);
	1037	+ show_rcu_gp_kthreads();
1037	1038	rcutorture_trace_dump();
1038	1039	}
1039	1040	rtcv_snap = rcu_torture_current_version;
...	...	@@ -280,6 +280,21 @@
280	280	EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
281	281
282	282	/*
	283	+ * Show the state of the grace-period kthreads.
	284	+ */
	285	+void show_rcu_gp_kthreads(void)
	286	+{
	287	+ struct rcu_state *rsp;
	288	+
	289	+ for_each_rcu_flavor(rsp) {
	290	+ pr_info("%s: wait state: %d ->state: %#lx\n",
	291	+ rsp->name, rsp->gp_state, rsp->gp_kthread->state);
	292	+ /* sched_show_task(rsp->gp_kthread); */
	293	+ }
	294	+}
	295	+EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads);
	296	+
	297	+/*
283	298	* Record the number of times rcutorture tests have been initiated and
284	299	* terminated. This information allows the debugfs tracing stats to be
285	300	* correlated to the rcutorture messages, even when the rcutorture module
...	...	@@ -1626,6 +1641,7 @@
1626	1641	trace_rcu_grace_period(rsp->name,
1627	1642	ACCESS_ONCE(rsp->gpnum),
1628	1643	TPS("reqwait"));
	1644	+ rsp->gp_state = RCU_GP_WAIT_GPS;
1629	1645	wait_event_interruptible(rsp->gp_wq,
1630	1646	ACCESS_ONCE(rsp->gp_flags) &
1631	1647	RCU_GP_FLAG_INIT);
...	...	@@ -1653,6 +1669,7 @@
1653	1669	trace_rcu_grace_period(rsp->name,
1654	1670	ACCESS_ONCE(rsp->gpnum),
1655	1671	TPS("fqswait"));
	1672	+ rsp->gp_state = RCU_GP_WAIT_FQS;
1656	1673	ret = wait_event_interruptible_timeout(rsp->gp_wq,
1657	1674	((gf = ACCESS_ONCE(rsp->gp_flags)) &
1658	1675	RCU_GP_FLAG_FQS) \|\|
...	...	@@ -406,7 +406,8 @@
406	406	unsigned long completed; /* # of last completed gp. */
407	407	struct task_struct gp_kthread; / Task for grace periods. */
408	408	wait_queue_head_t gp_wq; /* Where GP task waits. */
409		- int gp_flags; /* Commands for GP task. */
	409	+ short gp_flags; /* Commands for GP task. */
	410	+ short gp_state; /* GP kthread sleep state. */
410	411
411	412	/* End of fields guarded by root rcu_node's lock. */
412	413
...	...	@@ -468,6 +469,11 @@
468	469	/* Values for rcu_state structure's gp_flags field. */
469	470	#define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */
470	471	#define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */
	472	+
	473	+/* Values for rcu_state structure's gp_flags field. */
	474	+#define RCU_GP_WAIT_INIT 0 /* Initial state. */
	475	+#define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */
	476	+#define RCU_GP_WAIT_FQS 2 /* Wait for force-quiescent-state time. */
471	477
472	478	extern struct list_head rcu_struct_flavors;
473	479