Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull RCU changes for v3.4 from Ingo Molnar.  The major features of this
series are:

 - making RCU more aggressive about entering dyntick-idle mode in order
   to improve energy efficiency

 - converting a few more call_rcu()s to kfree_rcu()s

 - applying a number of rcutree fixes and cleanups to rcutiny

 - removing CONFIG_SMP #ifdefs from treercu

 - allowing RCU CPU stall times to be set via sysfs

 - adding CPU-stall capability to rcutorture

 - adding more RCU-abuse diagnostics

 - updating documentation

 - fixing yet more issues located by the still-ongoing top-to-bottom
   inspection of RCU, this time with a special focus on the CPU-hotplug
   code path.

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (48 commits)
  rcu: Stop spurious warnings from synchronize_sched_expedited
  rcu: Hold off RCU_FAST_NO_HZ after timer posted
  rcu: Eliminate softirq-mediated RCU_FAST_NO_HZ idle-entry loop
  rcu: Add RCU_NONIDLE() for idle-loop RCU read-side critical sections
  rcu: Allow nesting of rcu_idle_enter() and rcu_idle_exit()
  rcu: Remove redundant check for rcu_head misalignment
  PTR_ERR should be called before its argument is cleared.
  rcu: Convert WARN_ON_ONCE() in rcu_lock_acquire() to lockdep
  rcu: Trace only after NULL-pointer check
  rcu: Call out dangers of expedited RCU primitives
  rcu: Rework detection of use of RCU by offline CPUs
  lockdep: Add CPU-idle/offline warning to lockdep-RCU splat
  rcu: No interrupt disabling for rcu_prepare_for_idle()
  rcu: Move synchronize_sched_expedited() to rcutree.c
  rcu: Check for illegal use of RCU from offlined CPUs
  rcu: Update stall-warning documentation
  rcu: Add CPU-stall capability to rcutorture
  rcu: Make documentation give more realistic rcutorture duration
  rcutorture: Permit holding off CPU-hotplug operations during boot
  rcu: Print scheduling-clock information on RCU CPU stall-warning messages
  ...

1 files changed, 86 insertions, 5 deletions

diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index a58ac285fc69..a89b381a8c6e 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -65,7 +65,10 @@ static int fqs_duration;	/* Duration of bursts (us), 0 to disable. */
 static int fqs_holdoff;		/* Hold time within burst (us). */
 static int fqs_stutter = 3;	/* Wait time between bursts (s). */
 static int onoff_interval;	/* Wait time between CPU hotplugs, 0=disable. */
+static int onoff_holdoff;	/* Seconds after boot before CPU hotplugs. */
 static int shutdown_secs;	/* Shutdown time (s).  <=0 for no shutdown. */
+static int stall_cpu;		/* CPU-stall duration (s).  0 for no stall. */
+static int stall_cpu_holdoff = 10; /* Time to wait until stall (s).  */
 static int test_boost = 1;	/* Test RCU prio boost: 0=no, 1=maybe, 2=yes. */
 static int test_boost_interval = 7; /* Interval between boost tests, seconds. */
 static int test_boost_duration = 4; /* Duration of each boost test, seconds. */
@@ -95,8 +98,14 @@ module_param(fqs_stutter, int, 0444);
 MODULE_PARM_DESC(fqs_stutter, "Wait time between fqs bursts (s)");
 module_param(onoff_interval, int, 0444);
 MODULE_PARM_DESC(onoff_interval, "Time between CPU hotplugs (s), 0=disable");
+module_param(onoff_holdoff, int, 0444);
+MODULE_PARM_DESC(onoff_holdoff, "Time after boot before CPU hotplugs (s)");
 module_param(shutdown_secs, int, 0444);
 MODULE_PARM_DESC(shutdown_secs, "Shutdown time (s), zero to disable.");
+module_param(stall_cpu, int, 0444);
+MODULE_PARM_DESC(stall_cpu, "Stall duration (s), zero to disable.");
+module_param(stall_cpu_holdoff, int, 0444);
+MODULE_PARM_DESC(stall_cpu_holdoff, "Time to wait before starting stall (s).");
 module_param(test_boost, int, 0444);
 MODULE_PARM_DESC(test_boost, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");
 module_param(test_boost_interval, int, 0444);
@@ -129,6 +138,7 @@ static struct task_struct *shutdown_task;
 #ifdef CONFIG_HOTPLUG_CPU
 static struct task_struct *onoff_task;
 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
+static struct task_struct *stall_task;
 
 #define RCU_TORTURE_PIPE_LEN 10
 
@@ -990,12 +1000,12 @@ static void rcu_torture_timer(unsigned long unused)
 				  rcu_read_lock_bh_held() ||
 				  rcu_read_lock_sched_held() ||
 				  srcu_read_lock_held(&srcu_ctl));
-	do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);
 	if (p == NULL) {
 		/* Leave because rcu_torture_writer is not yet underway */
 		cur_ops->readunlock(idx);
 		return;
 	}
+	do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);
 	if (p->rtort_mbtest == 0)
 		atomic_inc(&n_rcu_torture_mberror);
 	spin_lock(&rand_lock);
@@ -1053,13 +1063,13 @@ rcu_torture_reader(void *arg)
 					  rcu_read_lock_bh_held() ||
 					  rcu_read_lock_sched_held() ||
 					  srcu_read_lock_held(&srcu_ctl));
-		do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);
 		if (p == NULL) {
 			/* Wait for rcu_torture_writer to get underway */
 			cur_ops->readunlock(idx);
 			schedule_timeout_interruptible(HZ);
 			continue;
 		}
+		do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);
 		if (p->rtort_mbtest == 0)
 			atomic_inc(&n_rcu_torture_mberror);
 		cur_ops->read_delay(&rand);
@@ -1300,13 +1310,13 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, char *tag)
 		"fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d "
 		"test_boost=%d/%d test_boost_interval=%d "
 		"test_boost_duration=%d shutdown_secs=%d "
-		"onoff_interval=%d\n",
+		"onoff_interval=%d onoff_holdoff=%d\n",
 		torture_type, tag, nrealreaders, nfakewriters,
 		stat_interval, verbose, test_no_idle_hz, shuffle_interval,
 		stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
 		test_boost, cur_ops->can_boost,
 		test_boost_interval, test_boost_duration, shutdown_secs,
-		onoff_interval);
+		onoff_interval, onoff_holdoff);
 }
 
 static struct notifier_block rcutorture_shutdown_nb = {
@@ -1410,6 +1420,11 @@ rcu_torture_onoff(void *arg)
 	for_each_online_cpu(cpu)
 		maxcpu = cpu;
 	WARN_ON(maxcpu < 0);
+	if (onoff_holdoff > 0) {
+		VERBOSE_PRINTK_STRING("rcu_torture_onoff begin holdoff");
+		schedule_timeout_interruptible(onoff_holdoff * HZ);
+		VERBOSE_PRINTK_STRING("rcu_torture_onoff end holdoff");
+	}
 	while (!kthread_should_stop()) {
 		cpu = (rcu_random(&rand) >> 4) % (maxcpu + 1);
 		if (cpu_online(cpu) && cpu_is_hotpluggable(cpu)) {
@@ -1450,12 +1465,15 @@ rcu_torture_onoff(void *arg)
 static int __cpuinit
 rcu_torture_onoff_init(void)
 {
+	int ret;
+
 	if (onoff_interval <= 0)
 		return 0;
 	onoff_task = kthread_run(rcu_torture_onoff, NULL, "rcu_torture_onoff");
 	if (IS_ERR(onoff_task)) {
+		ret = PTR_ERR(onoff_task);
 		onoff_task = NULL;
-		return PTR_ERR(onoff_task);
+		return ret;
 	}
 	return 0;
 }
@@ -1481,6 +1499,63 @@ static void rcu_torture_onoff_cleanup(void)
 
 #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
 
+/*
+ * CPU-stall kthread.  It waits as specified by stall_cpu_holdoff, then
+ * induces a CPU stall for the time specified by stall_cpu.
+ */
+static int __cpuinit rcu_torture_stall(void *args)
+{
+	unsigned long stop_at;
+
+	VERBOSE_PRINTK_STRING("rcu_torture_stall task started");
+	if (stall_cpu_holdoff > 0) {
+		VERBOSE_PRINTK_STRING("rcu_torture_stall begin holdoff");
+		schedule_timeout_interruptible(stall_cpu_holdoff * HZ);
+		VERBOSE_PRINTK_STRING("rcu_torture_stall end holdoff");
+	}
+	if (!kthread_should_stop()) {
+		stop_at = get_seconds() + stall_cpu;
+		/* RCU CPU stall is expected behavior in following code. */
+		printk(KERN_ALERT "rcu_torture_stall start.\n");
+		rcu_read_lock();
+		preempt_disable();
+		while (ULONG_CMP_LT(get_seconds(), stop_at))
+			continue;  /* Induce RCU CPU stall warning. */
+		preempt_enable();
+		rcu_read_unlock();
+		printk(KERN_ALERT "rcu_torture_stall end.\n");
+	}
+	rcutorture_shutdown_absorb("rcu_torture_stall");
+	while (!kthread_should_stop())
+		schedule_timeout_interruptible(10 * HZ);
+	return 0;
+}
+
+/* Spawn CPU-stall kthread, if stall_cpu specified. */
+static int __init rcu_torture_stall_init(void)
+{
+	int ret;
+
+	if (stall_cpu <= 0)
+		return 0;
+	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;
+	}
+	return 0;
+}
+
+/* Clean up after the CPU-stall kthread, if one was spawned. */
+static void rcu_torture_stall_cleanup(void)
+{
+	if (stall_task == NULL)
+		return;
+	VERBOSE_PRINTK_STRING("Stopping rcu_torture_stall_task.");
+	kthread_stop(stall_task);
+}
+
 static int rcutorture_cpu_notify(struct notifier_block *self,
 				 unsigned long action, void *hcpu)
 {
@@ -1523,6 +1598,7 @@ rcu_torture_cleanup(void)
 	fullstop = FULLSTOP_RMMOD;
 	mutex_unlock(&fullstop_mutex);
 	unregister_reboot_notifier(&rcutorture_shutdown_nb);
+	rcu_torture_stall_cleanup();
 	if (stutter_task) {
 		VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task");
 		kthread_stop(stutter_task);
@@ -1602,6 +1678,10 @@ rcu_torture_cleanup(void)
 		cur_ops->cleanup();
 	if (atomic_read(&n_rcu_torture_error))
 		rcu_torture_print_module_parms(cur_ops, "End of test: FAILURE");
+	else if (n_online_successes != n_online_attempts ||
+		 n_offline_successes != n_offline_attempts)
+		rcu_torture_print_module_parms(cur_ops,
+					       "End of test: RCU_HOTPLUG");
 	else
 		rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS");
 }
@@ -1819,6 +1899,7 @@ rcu_torture_init(void)
 	}
 	rcu_torture_onoff_init();
 	register_reboot_notifier(&rcutorture_shutdown_nb);
+	rcu_torture_stall_init();
 	rcutorture_record_test_transition();
 	mutex_unlock(&fullstop_mutex);
 	return 0;