---

yaml
---
r: 323534
b: refs/heads/master
c: e3ebfb9
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 60f53782c51f27c695840ce90c6c432284319eef
+refs/heads/master: e3ebfb96f396731ca2d0b108785d5da31b53ab00

trunk/Documentation/RCU/checklist.txt

@@ -310,12 +310,6 @@ over a rather long period of time, but improvements are always welcome!
 	code under the influence of preempt_disable(), you instead
 	need to use synchronize_irq() or synchronize_sched().
 
-	This same limitation also applies to synchronize_rcu_bh()
-	and synchronize_srcu(), as well as to the asynchronous and
-	expedited forms of the three primitives, namely call_rcu(),
-	call_rcu_bh(), call_srcu(), synchronize_rcu_expedited(),
-	synchronize_rcu_bh_expedited(), and synchronize_srcu_expedited().
-
 12.	Any lock acquired by an RCU callback must be acquired elsewhere
 	with softirq disabled, e.g., via spin_lock_irqsave(),
 	spin_lock_bh(), etc.  Failing to disable irq on a given

trunk/Documentation/RCU/whatisRCU.txt

@@ -873,7 +873,7 @@ d.	Do you need to treat NMI handlers, hardirq handlers,
 	and code segments with preemption disabled (whether
 	via preempt_disable(), local_irq_save(), local_bh_disable(),
 	or some other mechanism) as if they were explicit RCU readers?
-	If so, RCU-sched is the only choice that will work for you.
+	If so, you need RCU-sched.
 
 e.	Do you need RCU grace periods to complete even in the face
 	of softirq monopolization of one or more of the CPUs?  For
@@ -884,12 +884,7 @@ f.	Is your workload too update-intensive for normal use of
 	RCU, but inappropriate for other synchronization mechanisms?
 	If so, consider SLAB_DESTROY_BY_RCU.  But please be careful!
 
-g.	Do you need read-side critical sections that are respected
-	even though they are in the middle of the idle loop, during
-	user-mode execution, or on an offlined CPU?  If so, SRCU is the
-	only choice that will work for you.
-
-h.	Otherwise, use RCU.
+g.	Otherwise, use RCU.
 
 Of course, this all assumes that you have determined that RCU is in fact
 the right tool for your job.

trunk/kernel/rcupdate.c

@@ -45,6 +45,7 @@
 #include <linux/mutex.h>
 #include <linux/export.h>
 #include <linux/hardirq.h>
+#include <linux/delay.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/rcu.h>
@@ -81,6 +82,9 @@ void __rcu_read_unlock(void)
 	} else {
 		barrier();  /* critical section before exit code. */
 		t->rcu_read_lock_nesting = INT_MIN;
+#ifdef CONFIG_PROVE_RCU_DELAY
+		udelay(10); /* Make preemption more probable. */
+#endif /* #ifdef CONFIG_PROVE_RCU_DELAY */
 		barrier();  /* assign before ->rcu_read_unlock_special load */
 		if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
 			rcu_read_unlock_special(t);

trunk/kernel/rcutorture.c

@@ -53,11 +53,10 @@ MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and Josh Triplett <josh@fre
 
 static int nreaders = -1;	/* # reader threads, defaults to 2*ncpus */
 static int nfakewriters = 4;	/* # fake writer threads */
-static int stat_interval = 60;	/* Interval between stats, in seconds. */
-				/*  Zero means "only at end of test". */
+static int stat_interval;	/* Interval between stats, in seconds. */
+				/*  Defaults to "only at end of test". */
 static bool verbose;		/* Print more debug info. */
-static bool test_no_idle_hz = true;
-				/* Test RCU support for tickless idle CPUs. */
+static bool test_no_idle_hz;	/* Test RCU's support for tickless idle CPUs. */
 static int shuffle_interval = 3; /* Interval between shuffles (in sec)*/
 static int stutter = 5;		/* Start/stop testing interval (in sec) */
 static int irqreader = 1;	/* RCU readers from irq (timers). */
@@ -120,11 +119,11 @@ MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, srcu)");
 
 #define TORTURE_FLAG "-torture:"
 #define PRINTK_STRING(s) \
-	do { pr_alert("%s" TORTURE_FLAG s "\n", torture_type); } while (0)
+	do { printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
 #define VERBOSE_PRINTK_STRING(s) \
-	do { if (verbose) pr_alert("%s" TORTURE_FLAG s "\n", torture_type); } while (0)
+	do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG s "\n", torture_type); } while (0)
 #define VERBOSE_PRINTK_ERRSTRING(s) \
-	do { if (verbose) pr_alert("%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
+	do { if (verbose) printk(KERN_ALERT "%s" TORTURE_FLAG "!!! " s "\n", torture_type); } while (0)
 
 static char printk_buf[4096];
 
@@ -177,14 +176,8 @@ static long n_rcu_torture_boosts;
 static long n_rcu_torture_timers;
 static long n_offline_attempts;
 static long n_offline_successes;
-static unsigned long sum_offline;
-static int min_offline = -1;
-static int max_offline;
 static long n_online_attempts;
 static long n_online_successes;
-static unsigned long sum_online;
-static int min_online = -1;
-static int max_online;
 static long n_barrier_attempts;
 static long n_barrier_successes;
 static struct list_head rcu_torture_removed;
@@ -242,7 +235,7 @@ rcutorture_shutdown_notify(struct notifier_block *unused1,
 	if (fullstop == FULLSTOP_DONTSTOP)
 		fullstop = FULLSTOP_SHUTDOWN;
 	else
-		pr_warn(/* but going down anyway, so... */
+		printk(KERN_WARNING /* but going down anyway, so... */
 		       "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
 	mutex_unlock(&fullstop_mutex);
 	return NOTIFY_DONE;
@@ -255,7 +248,7 @@ rcutorture_shutdown_notify(struct notifier_block *unused1,
 static void rcutorture_shutdown_absorb(char *title)
 {
 	if (ACCESS_ONCE(fullstop) == FULLSTOP_SHUTDOWN) {
-		pr_notice(
+		printk(KERN_NOTICE
 		       "rcutorture thread %s parking due to system shutdown\n",
 		       title);
 		schedule_timeout_uninterruptible(MAX_SCHEDULE_TIMEOUT);
@@ -1221,13 +1214,11 @@ rcu_torture_printk(char *page)
 		       n_rcu_torture_boost_failure,
 		       n_rcu_torture_boosts,
 		       n_rcu_torture_timers);
-	cnt += sprintf(&page[cnt],
-		       "onoff: %ld/%ld:%ld/%ld %d,%d:%d,%d %lu:%lu (HZ=%d) ",
-		       n_online_successes, n_online_attempts,
-		       n_offline_successes, n_offline_attempts,
-		       min_online, max_online,
-		       min_offline, max_offline,
-		       sum_online, sum_offline, HZ);
+	cnt += sprintf(&page[cnt], "onoff: %ld/%ld:%ld/%ld ",
+		       n_online_successes,
+		       n_online_attempts,
+		       n_offline_successes,
+		       n_offline_attempts);
 	cnt += sprintf(&page[cnt], "barrier: %ld/%ld:%ld",
 		       n_barrier_successes,
 		       n_barrier_attempts,
@@ -1276,7 +1267,7 @@ rcu_torture_stats_print(void)
 	int cnt;
 
 	cnt = rcu_torture_printk(printk_buf);
-	pr_alert("%s", printk_buf);
+	printk(KERN_ALERT "%s", printk_buf);
 }
 
 /*
@@ -1389,20 +1380,20 @@ rcu_torture_stutter(void *arg)
 static inline void
 rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, char *tag)
 {
-	pr_alert("%s" TORTURE_FLAG
-		 "--- %s: nreaders=%d nfakewriters=%d "
-		 "stat_interval=%d verbose=%d test_no_idle_hz=%d "
-		 "shuffle_interval=%d stutter=%d irqreader=%d "
-		 "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 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_holdoff);
+	printk(KERN_ALERT "%s" TORTURE_FLAG
+		"--- %s: nreaders=%d nfakewriters=%d "
+		"stat_interval=%d verbose=%d test_no_idle_hz=%d "
+		"shuffle_interval=%d stutter=%d irqreader=%d "
+		"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 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_holdoff);
 }
 
 static struct notifier_block rcutorture_shutdown_nb = {
@@ -1469,9 +1460,9 @@ rcu_torture_shutdown(void *arg)
 	       !kthread_should_stop()) {
 		delta = shutdown_time - jiffies_snap;
 		if (verbose)
-			pr_alert("%s" TORTURE_FLAG
-				 "rcu_torture_shutdown task: %lu jiffies remaining\n",
-				 torture_type, delta);
+			printk(KERN_ALERT "%s" TORTURE_FLAG
+			       "rcu_torture_shutdown task: %lu jiffies remaining\n",
+			       torture_type, delta);
 		schedule_timeout_interruptible(delta);
 		jiffies_snap = ACCESS_ONCE(jiffies);
 	}
@@ -1499,10 +1490,8 @@ static int __cpuinit
 rcu_torture_onoff(void *arg)
 {
 	int cpu;
-	unsigned long delta;
 	int maxcpu = -1;
 	DEFINE_RCU_RANDOM(rand);
-	unsigned long starttime;
 
 	VERBOSE_PRINTK_STRING("rcu_torture_onoff task started");
 	for_each_online_cpu(cpu)
@@ -1517,51 +1506,29 @@ rcu_torture_onoff(void *arg)
 		cpu = (rcu_random(&rand) >> 4) % (maxcpu + 1);
 		if (cpu_online(cpu) && cpu_is_hotpluggable(cpu)) {
 			if (verbose)
-				pr_alert("%s" TORTURE_FLAG
-					 "rcu_torture_onoff task: offlining %d\n",
-					 torture_type, cpu);
-			starttime = jiffies;
+				printk(KERN_ALERT "%s" TORTURE_FLAG
+				       "rcu_torture_onoff task: offlining %d\n",
+				       torture_type, cpu);
 			n_offline_attempts++;
 			if (cpu_down(cpu) == 0) {
 				if (verbose)
-					pr_alert("%s" TORTURE_FLAG
-						 "rcu_torture_onoff task: offlined %d\n",
-						 torture_type, cpu);
+					printk(KERN_ALERT "%s" TORTURE_FLAG
+					       "rcu_torture_onoff task: offlined %d\n",
+					       torture_type, cpu);
 				n_offline_successes++;
-				delta = jiffies - starttime;
-				sum_offline += delta;
-				if (min_offline < 0) {
-					min_offline = delta;
-					max_offline = delta;
-				}
-				if (min_offline > delta)
-					min_offline = delta;
-				if (max_offline < delta)
-					max_offline = delta;
 			}
 		} else if (cpu_is_hotpluggable(cpu)) {
 			if (verbose)
-				pr_alert("%s" TORTURE_FLAG
-					 "rcu_torture_onoff task: onlining %d\n",
-					 torture_type, cpu);
-			starttime = jiffies;
+				printk(KERN_ALERT "%s" TORTURE_FLAG
+				       "rcu_torture_onoff task: onlining %d\n",
+				       torture_type, cpu);
 			n_online_attempts++;
 			if (cpu_up(cpu) == 0) {
 				if (verbose)
-					pr_alert("%s" TORTURE_FLAG
-						 "rcu_torture_onoff task: onlined %d\n",
-						 torture_type, cpu);
+					printk(KERN_ALERT "%s" TORTURE_FLAG
+					       "rcu_torture_onoff task: onlined %d\n",
+					       torture_type, cpu);
 				n_online_successes++;
-				delta = jiffies - starttime;
-				sum_online += delta;
-				if (min_online < 0) {
-					min_online = delta;
-					max_online = delta;
-				}
-				if (min_online > delta)
-					min_online = delta;
-				if (max_online < delta)
-					max_online = delta;
 			}
 		}
 		schedule_timeout_interruptible(onoff_interval * HZ);
@@ -1626,14 +1593,14 @@ static int __cpuinit rcu_torture_stall(void *args)
 	if (!kthread_should_stop()) {
 		stop_at = get_seconds() + stall_cpu;
 		/* RCU CPU stall is expected behavior in following code. */
-		pr_alert("rcu_torture_stall start.\n");
+		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();
-		pr_alert("rcu_torture_stall end.\n");
+		printk(KERN_ALERT "rcu_torture_stall end.\n");
 	}
 	rcutorture_shutdown_absorb("rcu_torture_stall");
 	while (!kthread_should_stop())
@@ -1749,12 +1716,12 @@ static int rcu_torture_barrier_init(void)
 	if (n_barrier_cbs == 0)
 		return 0;
 	if (cur_ops->call == NULL || cur_ops->cb_barrier == NULL) {
-		pr_alert("%s" TORTURE_FLAG
-			 " Call or barrier ops missing for %s,\n",
-			 torture_type, cur_ops->name);
-		pr_alert("%s" TORTURE_FLAG
-			 " RCU barrier testing omitted from run.\n",
-			 torture_type);
+		printk(KERN_ALERT "%s" TORTURE_FLAG
+		       " Call or barrier ops missing for %s,\n",
+		       torture_type, cur_ops->name);
+		printk(KERN_ALERT "%s" TORTURE_FLAG
+		       " RCU barrier testing omitted from run.\n",
+		       torture_type);
 		return 0;
 	}
 	atomic_set(&barrier_cbs_count, 0);
@@ -1847,7 +1814,7 @@ rcu_torture_cleanup(void)
 	mutex_lock(&fullstop_mutex);
 	rcutorture_record_test_transition();
 	if (fullstop == FULLSTOP_SHUTDOWN) {
-		pr_warn(/* but going down anyway, so... */
+		printk(KERN_WARNING /* but going down anyway, so... */
 		       "Concurrent 'rmmod rcutorture' and shutdown illegal!\n");
 		mutex_unlock(&fullstop_mutex);
 		schedule_timeout_uninterruptible(10);
@@ -1971,17 +1938,17 @@ rcu_torture_init(void)
 			break;
 	}
 	if (i == ARRAY_SIZE(torture_ops)) {
-		pr_alert("rcu-torture: invalid torture type: \"%s\"\n",
-			 torture_type);
-		pr_alert("rcu-torture types:");
+		printk(KERN_ALERT "rcu-torture: invalid torture type: \"%s\"\n",
+		       torture_type);
+		printk(KERN_ALERT "rcu-torture types:");
 		for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
-			pr_alert(" %s", torture_ops[i]->name);
-		pr_alert("\n");
+			printk(KERN_ALERT " %s", torture_ops[i]->name);
+		printk(KERN_ALERT "\n");
 		mutex_unlock(&fullstop_mutex);
 		return -EINVAL;
 	}
 	if (cur_ops->fqs == NULL && fqs_duration != 0) {
-		pr_alert("rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n");
+		printk(KERN_ALERT "rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n");
 		fqs_duration = 0;
 	}
 	if (cur_ops->init)
@@ -2029,15 +1996,14 @@ rcu_torture_init(void)
 	/* Start up the kthreads. */
 
 	VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
-	writer_task = kthread_create(rcu_torture_writer, NULL,
-				     "rcu_torture_writer");
+	writer_task = kthread_run(rcu_torture_writer, NULL,
+				  "rcu_torture_writer");
 	if (IS_ERR(writer_task)) {
 		firsterr = PTR_ERR(writer_task);
 		VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
 		writer_task = NULL;
 		goto unwind;
 	}
-	wake_up_process(writer_task);
 	fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
 				   GFP_KERNEL);
 	if (fakewriter_tasks == NULL) {
@@ -2152,15 +2118,14 @@ rcu_torture_init(void)
 	}
 	if (shutdown_secs > 0) {
 		shutdown_time = jiffies + shutdown_secs * HZ;
-		shutdown_task = kthread_create(rcu_torture_shutdown, NULL,
-					       "rcu_torture_shutdown");
+		shutdown_task = kthread_run(rcu_torture_shutdown, NULL,
+					    "rcu_torture_shutdown");
 		if (IS_ERR(shutdown_task)) {
 			firsterr = PTR_ERR(shutdown_task);
 			VERBOSE_PRINTK_ERRSTRING("Failed to create shutdown");
 			shutdown_task = NULL;
 			goto unwind;
 		}
-		wake_up_process(shutdown_task);
 	}
 	i = rcu_torture_onoff_init();
 	if (i != 0) {

trunk/lib/Kconfig.debug

@@ -629,6 +629,20 @@ config PROVE_RCU_REPEATEDLY
 
 	 Say N if you are unsure.
 
+config PROVE_RCU_DELAY
+	bool "RCU debugging: preemptible RCU race provocation"
+	depends on DEBUG_KERNEL && PREEMPT_RCU
+	default n
+	help
+	 There is a class of races that involve an unlikely preemption
+	 of __rcu_read_unlock() just after ->rcu_read_lock_nesting has
+	 been set to INT_MIN.  This feature inserts a delay at that
+	 point to increase the probability of these races.
+
+	 Say Y to increase probability of preemption of __rcu_read_unlock().
+
+	 Say N if you are unsure.
+
 config SPARSE_RCU_POINTER
 	bool "RCU debugging: sparse-based checks for pointer usage"
 	default n