[RFC PATCH 11/12] locking/selftest: Exercise hardirq return-tail preparation

[Karl Mehltretter <kmehltretter@gmail.com>]

The return-tail lockdep preparation must accept exactly one live
hardirq context. Zero and nested contexts must fail, and the ordinary
preparation helper must continue to reject a live hardirq context.

Add focused boot-time lockdep cases for those four states. Skip the
final IRQ-state transition after an expected preparation failure so
that each failure remains attributable to the preparation invariant.

Assisted-by: LLM
---
 lib/locking-selftest.c | 53 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index c3d976c801bb4..1575a04f65d46 100644
--- a/lib/locking-selftest.c
+++ b/lib/locking-selftest.c
@@ -222,6 +222,55 @@ static void init_shared_classes(void)
 		local_irq_enable();		\
 		local_bh_enable();
 
+static void irqtail_prepare_test_enter(unsigned int nr)
+{
+	unsigned int i;
+
+	local_irq_disable();
+	for (i = 0; i < nr; i++)
+		__irq_enter_raw();
+	trace_hardirqs_on_prepare();
+}
+
+static void irqtail_prepare_test_exit(unsigned int nr)
+{
+	unsigned int i;
+
+	for (i = 0; i < nr; i++)
+		__irq_exit_raw();
+	if (debug_locks)
+		lockdep_hardirqs_on(_THIS_IP_);
+	raw_local_irq_enable();
+}
+
+static void prepare_irqtail_0(void)
+{
+	irqtail_prepare_test_enter(0);
+	lockdep_hardirqs_on_prepare_irqtail();
+	irqtail_prepare_test_exit(0);
+}
+
+static void prepare_irqtail_1(void)
+{
+	irqtail_prepare_test_enter(1);
+	lockdep_hardirqs_on_prepare_irqtail();
+	irqtail_prepare_test_exit(1);
+}
+
+static void prepare_irqtail_2(void)
+{
+	irqtail_prepare_test_enter(2);
+	lockdep_hardirqs_on_prepare_irqtail();
+	irqtail_prepare_test_exit(2);
+}
+
+static void prepare_regular_1(void)
+{
+	irqtail_prepare_test_enter(1);
+	lockdep_hardirqs_on_prepare();
+	irqtail_prepare_test_exit(1);
+}
+
 /*
  * Shortcuts for lock/unlock API variants, to keep
  * the testcases compact:
@@ -2934,6 +2983,10 @@ void locking_selftest(void)
 	DO_TESTCASE_6x2x2RW("irq read-recursion", irq_read_recursion);
 	DO_TESTCASE_6x2x2RW("irq read-recursion #2", irq_read_recursion2);
 	DO_TESTCASE_6x2x2RW("irq read-recursion #3", irq_read_recursion3);
+	DO_TESTCASE_1B("IRQ tail prepare", prepare_irqtail, 0);
+	DO_TESTCASE_1("IRQ tail prepare", prepare_irqtail, 1);
+	DO_TESTCASE_1B("IRQ tail prepare", prepare_irqtail, 2);
+	DO_TESTCASE_1B("regular IRQ prepare", prepare_regular, 1);
 
 	ww_tests();
 
-- 
2.39.5 (Apple Git-154)