[PATCH RFC v3 12/15] hazptrtorture: add slowpath and lockdep scenarios

[Kunwu Chan <kunwu.chan@gmail.com>]

Add a wq_churn kthread and module parameter to exercise lockdep
dynamic-key handling by repeatedly creating and destroying
workqueues.  Each workqueue creation registers a dynamic lock
class key and each destruction unregisters it, exercising both
is_dynamic_key() and lockdep_unregister_key().

Add SLOWPATH and LOCKDEP torture scenarios to exercise the
hazptr acquire slow path, including its use by lockdep under
CONFIG_PROVE_LOCKING.

Add both scenarios to CFLIST so that torture.sh --do-hazptr
includes them.

Signed-off-by: Kunwu Chan <kunwu.chan@gmail.com>
---
 kernel/rcu/hazptrtorture.c                    | 57 +++++++++++++++++--
 .../rcutorture/configs/hazptr/CFLIST          |  2 +
 .../rcutorture/configs/hazptr/LOCKDEP         | 17 ++++++
 .../rcutorture/configs/hazptr/LOCKDEP.boot    |  1 +
 .../rcutorture/configs/hazptr/SLOWPATH        | 16 ++++++
 5 files changed, 89 insertions(+), 4 deletions(-)
 create mode 100644 tools/testing/selftests/rcutorture/configs/hazptr/LOCKDEP
 create mode 100644 tools/testing/selftests/rcutorture/configs/hazptr/LOCKDEP.boot
 create mode 100644 tools/testing/selftests/rcutorture/configs/hazptr/SLOWPATH

diff --git a/kernel/rcu/hazptrtorture.c b/kernel/rcu/hazptrtorture.c
index 7c8b5899fb01..7c144b9bca6a 100644
--- a/kernel/rcu/hazptrtorture.c
+++ b/kernel/rcu/hazptrtorture.c
@@ -23,6 +23,7 @@
 #include <linux/torture.h>
 #include <linux/hazptr.h>
 #include <linux/rcupdate.h>
+#include <linux/workqueue.h>
 
 #include "rcu.h"
 
@@ -49,6 +50,8 @@ torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable.");
 torture_param(int, stat_interval, 60, "Number of seconds between stats printk()s");
 torture_param(int, stutter, 5, "Number of seconds to run/halt test");
 torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
+torture_param(bool, wq_churn, false,
+	      "Churn workqueues to exercise lockdep dynamic keys");
 
 static char *torture_type = "hazptr";
 module_param(torture_type, charp, 0444);
@@ -60,6 +63,7 @@ static struct task_struct *preempt_task;
 static struct task_struct **reader_tasks;
 static struct task_struct *do_pending_task;
 static struct task_struct *stats_task;
+static struct task_struct *wq_churn_task;
 
 #define HAZPTR_TORTURE_PIPE_LEN 10
 
@@ -87,6 +91,7 @@ static DEFINE_PER_CPU(atomic_long_t, hazptr_torture_acquires_irq);
 static DEFINE_PER_CPU(atomic_long_t, hazptr_torture_releases_irq);
 static DEFINE_PER_CPU(atomic_long_t, hazptr_torture_releases_defer);
 static DEFINE_PER_CPU(atomic_long_t, hazptr_torture_releases_undefer);
+static atomic_t n_hazptr_torture_wq_churn;
 static struct list_head hazptr_torture_removed;
 
 // State for a deferred (AKA pending) hazard pointer
@@ -643,13 +648,14 @@ hazptr_torture_stats_print(void)
 		atomic_read(&n_hazptr_torture_alloc_fail),
 		atomic_read(&n_hazptr_torture_free));
 	torture_onoff_stats();
-	pr_cont("acq: %lld rel: %lld acqirq: %lld relirq: %lld reldefer: %lld relundefer %lld\n",
+	pr_cont("acq: %lld rel: %lld acqirq: %lld relirq: %lld reldefer: %lld relundefer %lld wqchurn: %d\n",
 		torture_sum_pcpu_atomic_long(&hazptr_torture_acquires),
 		torture_sum_pcpu_atomic_long(&hazptr_torture_releases),
 		torture_sum_pcpu_atomic_long(&hazptr_torture_acquires_irq),
 		torture_sum_pcpu_atomic_long(&hazptr_torture_releases_irq),
 		torture_sum_pcpu_atomic_long(&hazptr_torture_releases_defer),
-		torture_sum_pcpu_atomic_long(&hazptr_torture_releases_undefer));
+		torture_sum_pcpu_atomic_long(&hazptr_torture_releases_undefer),
+		atomic_read(&n_hazptr_torture_wq_churn));
 
 	pr_alert("%s%s ", torture_type, TORTURE_FLAG);
 	if (i > 1) {
@@ -720,14 +726,14 @@ hazptr_torture_print_module_parms(struct hazptr_torture_ops *cur_ops, const char
 		 "defer_modulus=%d irq_acquire=%d irq_release=%d kthread_do_pending_ms=%d "
 		 "onoff_interval=%d onoff_holdoff=%d "
 		 "preempt_duration=%d preempt_interval=%d "
-		 "reader_sleep_us=%d "
+		 "reader_sleep_us=%d wq_churn=%d "
 		 "shuffle_interval=%d shutdown_secs=%d stat_interval=%d stutter=%d "
 		 "verbose=%d\n",
 		 torture_type, tag, nrealreaders, nwriters,
 		 defer_modulus, irq_acquire, irq_release, kthread_do_pending_ms,
 		 onoff_interval, onoff_holdoff,
 		 preempt_duration, preempt_interval,
-		 reader_sleep_us,
+		 reader_sleep_us, wq_churn,
 		 shuffle_interval, shutdown_secs, stat_interval, stutter,
 		 verbose);
 }
@@ -761,6 +767,42 @@ static int hazptr_torture_preempt(void *unused)
 	return 0;
 }
 
+static void hazptr_torture_wq_churn_fn(struct work_struct *work)
+{
+}
+
+/*
+ * Repeatedly create and destroy workqueues.  Each workqueue creation
+ * registers a lockdep dynamic key and each destruction unregisters it,
+ * which exercises both is_dynamic_key() and lockdep_unregister_key(),
+ * the two lockdep paths that use hazptr.  Most useful in kernels with
+ * CONFIG_PROVE_LOCKING=y and CONFIG_HAZPTR_ACQUIRE_FORCE_SLOWPATH=y.
+ */
+static int hazptr_torture_wq_churn(void *unused)
+{
+	DEFINE_TORTURE_RANDOM(rand);
+
+	VERBOSE_TOROUT_STRING("hazptr_torture_wq_churn task started");
+	do {
+		struct workqueue_struct *wq;
+		struct work_struct churn_work;
+
+		wq = alloc_workqueue("hazptr-torture-churn", WQ_PERCPU, 1);
+		if (!wq) {
+			torture_hrtimeout_ms(10, 10, &rand);
+			continue;
+		}
+		INIT_WORK(&churn_work, hazptr_torture_wq_churn_fn);
+		queue_work(wq, &churn_work);
+		flush_work(&churn_work);
+		destroy_workqueue(wq);
+		atomic_inc(&n_hazptr_torture_wq_churn);
+		stutter_wait("hazptr_torture_wq_churn");
+	} while (!torture_must_stop());
+	torture_kthread_stopping("hazptr_torture_wq_churn");
+	return 0;
+}
+
 static void
 hazptr_torture_cleanup(void)
 {
@@ -775,6 +817,7 @@ hazptr_torture_cleanup(void)
 
 	torture_stop_kthread(hazptr_torture_do_pending, do_pending_task);
 	torture_stop_kthread(hazptr_torture_preempt, preempt_task);
+	torture_stop_kthread(hazptr_torture_wq_churn, wq_churn_task);
 	torture_stop_kthread(hazptr_torture_writer, writer_task);
 
 	if (reader_tasks) {
@@ -853,6 +896,7 @@ static int __init hazptr_torture_init(void)
 	atomic_set(&n_hazptr_torture_alloc_fail, 0);
 	atomic_set(&n_hazptr_torture_free, 0);
 	atomic_set(&n_hazptr_torture_error, 0);
+	atomic_set(&n_hazptr_torture_wq_churn, 0);
 	for (i = 0; i < HAZPTR_TORTURE_PIPE_LEN + 1; i++)
 		atomic_set(&hazptr_torture_wcount[i], 0);
 	for_each_possible_cpu(cpu) {
@@ -928,6 +972,11 @@ static int __init hazptr_torture_init(void)
 		if (torture_init_error(firsterr))
 			goto unwind;
 	}
+	if (wq_churn) {
+		firsterr = torture_create_kthread(hazptr_torture_wq_churn, NULL, wq_churn_task);
+		if (torture_init_error(firsterr))
+			goto unwind;
+	}
 
 	torture_init_end();
 	return 0;
diff --git a/tools/testing/selftests/rcutorture/configs/hazptr/CFLIST b/tools/testing/selftests/rcutorture/configs/hazptr/CFLIST
index 4d62eb4a39f9..380b8402ccc9 100644
--- a/tools/testing/selftests/rcutorture/configs/hazptr/CFLIST
+++ b/tools/testing/selftests/rcutorture/configs/hazptr/CFLIST
@@ -1,2 +1,4 @@
 NOPREEMPT
 PREEMPT
+SLOWPATH
+LOCKDEP
diff --git a/tools/testing/selftests/rcutorture/configs/hazptr/LOCKDEP b/tools/testing/selftests/rcutorture/configs/hazptr/LOCKDEP
new file mode 100644
index 000000000000..129769e2e32e
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/hazptr/LOCKDEP
@@ -0,0 +1,17 @@
+CONFIG_SMP=y
+CONFIG_NR_CPUS=16
+CONFIG_PREEMPT_NONE=n
+CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT=y
+CONFIG_HZ_PERIODIC=n
+CONFIG_NO_HZ_IDLE=y
+CONFIG_NO_HZ_FULL=n
+CONFIG_HOTPLUG_CPU=y
+CONFIG_SUSPEND=n
+CONFIG_HIBERNATION=n
+CONFIG_DEBUG_LOCK_ALLOC=y
+CONFIG_PROVE_LOCKING=y
+CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
+CONFIG_DEBUG_KERNEL=y
+CONFIG_HAZPTR_DEBUG=y
+CONFIG_HAZPTR_ACQUIRE_FORCE_SLOWPATH=y
diff --git a/tools/testing/selftests/rcutorture/configs/hazptr/LOCKDEP.boot b/tools/testing/selftests/rcutorture/configs/hazptr/LOCKDEP.boot
new file mode 100644
index 000000000000..7b16720214bd
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/hazptr/LOCKDEP.boot
@@ -0,0 +1 @@
+hazptrtorture.wq_churn=1
diff --git a/tools/testing/selftests/rcutorture/configs/hazptr/SLOWPATH b/tools/testing/selftests/rcutorture/configs/hazptr/SLOWPATH
new file mode 100644
index 000000000000..4d13028ca84c
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/hazptr/SLOWPATH
@@ -0,0 +1,16 @@
+CONFIG_SMP=y
+CONFIG_NR_CPUS=16
+CONFIG_PREEMPT_NONE=n
+CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT=y
+CONFIG_HZ_PERIODIC=n
+CONFIG_NO_HZ_IDLE=y
+CONFIG_NO_HZ_FULL=n
+CONFIG_HOTPLUG_CPU=y
+CONFIG_SUSPEND=n
+CONFIG_HIBERNATION=n
+CONFIG_PROVE_LOCKING=n
+CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
+CONFIG_DEBUG_KERNEL=y
+CONFIG_HAZPTR_DEBUG=y
+CONFIG_HAZPTR_ACQUIRE_FORCE_SLOWPATH=y
-- 
2.43.0