[PATCH v4 05/14] rcutorture: Add test code for call_rcu_lazy()

["Joel Fernandes (Google)" <joel@joelfernandes.org>]

We add a new RCU type to test call_rcu_lazy(). This allows us to just
override the '.call' callback. To compensate for the laziness, we force
the laziness to a small number of jiffies. The idea of this test is to
stress the new code paths for stability and ensure it at least is providing
behavior in parity with, or similar to, call_rcu(). The actual check for
amount of laziness is in another test (rcuscale).

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 kernel/rcu/rcu.h                              |  1 +
 kernel/rcu/rcutorture.c                       | 60 ++++++++++++++++++-
 kernel/rcu/tree.c                             |  1 +
 .../selftests/rcutorture/configs/rcu/CFLIST   |  1 +
 .../selftests/rcutorture/configs/rcu/TREE11   | 18 ++++++
 .../rcutorture/configs/rcu/TREE11.boot        |  8 +++
 6 files changed, 88 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/TREE11
 create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/TREE11.boot

diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 608f6ab76c7f..aa3243e49506 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -460,6 +460,7 @@ enum rcutorture_type {
 	RCU_TASKS_TRACING_FLAVOR,
 	RCU_TRIVIAL_FLAVOR,
 	SRCU_FLAVOR,
+	RCU_LAZY_FLAVOR,
 	INVALID_RCU_FLAVOR
 };
 
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 7120165a9342..c52cc4c064f9 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -872,6 +872,64 @@ static struct rcu_torture_ops tasks_rude_ops = {
 
 #endif // #else #ifdef CONFIG_TASKS_RUDE_RCU
 
+#ifdef CONFIG_RCU_LAZY
+
+/*
+ * Definitions for lazy RCU torture testing.
+ */
+static unsigned long orig_jiffies_till_flush;
+
+static void rcu_sync_torture_init_lazy(void)
+{
+	rcu_sync_torture_init();
+
+	orig_jiffies_till_flush = rcu_lazy_get_jiffies_till_flush();
+	rcu_lazy_set_jiffies_till_flush(50);
+}
+
+static void rcu_lazy_cleanup(void)
+{
+	rcu_lazy_set_jiffies_till_flush(orig_jiffies_till_flush);
+}
+
+static struct rcu_torture_ops rcu_lazy_ops = {
+	.ttype			= RCU_LAZY_FLAVOR,
+	.init			= rcu_sync_torture_init_lazy,
+	.cleanup		= rcu_lazy_cleanup,
+	.readlock		= rcu_torture_read_lock,
+	.read_delay		= rcu_read_delay,
+	.readunlock		= rcu_torture_read_unlock,
+	.readlock_held		= torture_readlock_not_held,
+	.get_gp_seq		= rcu_get_gp_seq,
+	.gp_diff		= rcu_seq_diff,
+	.deferred_free		= rcu_torture_deferred_free,
+	.sync			= synchronize_rcu,
+	.exp_sync		= synchronize_rcu_expedited,
+	.get_gp_state		= get_state_synchronize_rcu,
+	.start_gp_poll		= start_poll_synchronize_rcu,
+	.poll_gp_state		= poll_state_synchronize_rcu,
+	.cond_sync		= cond_synchronize_rcu,
+	.call			= call_rcu_lazy,
+	.cb_barrier		= rcu_barrier,
+	.fqs			= rcu_force_quiescent_state,
+	.stats			= NULL,
+	.gp_kthread_dbg		= show_rcu_gp_kthreads,
+	.check_boost_failed	= rcu_check_boost_fail,
+	.stall_dur		= rcu_jiffies_till_stall_check,
+	.irq_capable		= 1,
+	.can_boost		= IS_ENABLED(CONFIG_RCU_BOOST),
+	.extendables		= RCUTORTURE_MAX_EXTEND,
+	.name			= "rcu_lazy"
+};
+
+#define LAZY_OPS &rcu_lazy_ops,
+
+#else // #ifdef CONFIG_RCU_LAZY
+
+#define LAZY_OPS
+
+#endif // #else #ifdef CONFIG_RCU_LAZY
+
 
 #ifdef CONFIG_TASKS_TRACE_RCU
 
@@ -3145,7 +3203,7 @@ rcu_torture_init(void)
 	unsigned long gp_seq = 0;
 	static struct rcu_torture_ops *torture_ops[] = {
 		&rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops, &busted_srcud_ops,
-		TASKS_OPS TASKS_RUDE_OPS TASKS_TRACING_OPS
+		TASKS_OPS TASKS_RUDE_OPS TASKS_TRACING_OPS LAZY_OPS
 		&trivial_ops,
 	};
 
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index e76fef8031be..67026382dc21 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -600,6 +600,7 @@ void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
 {
 	switch (test_type) {
 	case RCU_FLAVOR:
+	case RCU_LAZY_FLAVOR:
 		*flags = READ_ONCE(rcu_state.gp_flags);
 		*gp_seq = rcu_seq_current(&rcu_state.gp_seq);
 		break;
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/CFLIST b/tools/testing/selftests/rcutorture/configs/rcu/CFLIST
index 98b6175e5aa0..609c3370616f 100644
--- a/tools/testing/selftests/rcutorture/configs/rcu/CFLIST
+++ b/tools/testing/selftests/rcutorture/configs/rcu/CFLIST
@@ -5,6 +5,7 @@ TREE04
 TREE05
 TREE07
 TREE09
+TREE11
 SRCU-N
 SRCU-P
 SRCU-T
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE11 b/tools/testing/selftests/rcutorture/configs/rcu/TREE11
new file mode 100644
index 000000000000..436013f3e015
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE11
@@ -0,0 +1,18 @@
+CONFIG_SMP=y
+CONFIG_PREEMPT_NONE=n
+CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT=y
+#CHECK#CONFIG_PREEMPT_RCU=y
+CONFIG_HZ_PERIODIC=n
+CONFIG_NO_HZ_IDLE=y
+CONFIG_NO_HZ_FULL=n
+CONFIG_RCU_TRACE=y
+CONFIG_HOTPLUG_CPU=y
+CONFIG_MAXSMP=y
+CONFIG_CPUMASK_OFFSTACK=y
+CONFIG_RCU_NOCB_CPU=y
+CONFIG_DEBUG_LOCK_ALLOC=n
+CONFIG_RCU_BOOST=n
+CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
+CONFIG_RCU_EXPERT=y
+CONFIG_RCU_LAZY=y
diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE11.boot b/tools/testing/selftests/rcutorture/configs/rcu/TREE11.boot
new file mode 100644
index 000000000000..9b6f720d4ccd
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE11.boot
@@ -0,0 +1,8 @@
+maxcpus=8 nr_cpus=43
+rcutree.gp_preinit_delay=3
+rcutree.gp_init_delay=3
+rcutree.gp_cleanup_delay=3
+rcu_nocbs=0-7
+rcutorture.torture_type=rcu_lazy
+rcutorture.nocbs_nthreads=8
+rcutorture.fwd_progress=0
-- 
2.37.2.609.g9ff673ca1a-goog