tests: add tests for waitqueue helpers.

Signed-off-by: Imran Khan <imran.f.khan@oracle.com>

tests/linux_kernel/helpers/test_wait.py

@@ -0,0 +1,30 @@
+# Copyright (c) 2023, Oracle and/or its affiliates.
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+from drgn.helpers.linux.wait import waitqueue_active, waitqueue_for_each_task
+from tests.linux_kernel import LinuxKernelTestCase, skip_unless_have_test_kmod
+
+
+def waiter_tasks(prog):
+    return [
+        prog["drgn_test_waitq_kthread"],
+    ]
+
+
+@skip_unless_have_test_kmod
+class TestWaitqueue(LinuxKernelTestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.waitq = cls.prog["drgn_test_waitq"].address_of_()
+        cls.empty_waitq = cls.prog["drgn_test_empty_waitq"].address_of_()
+
+    def test_waitqueue_active(self):
+        self.assertTrue(waitqueue_active(self.waitq))
+        self.assertFalse(waitqueue_active(self.empty_waitq))
+
+    def test_waitqueue_for_each_task(self):
+        self.assertEqual(list(waitqueue_for_each_task(self.empty_waitq)), [])
+        self.assertEqual(
+            [task for task in waitqueue_for_each_task(self.waitq)],
+            waiter_tasks(self.prog),
+        )

tests/linux_kernel/kmod/drgn_test.c

@@ -25,6 +25,7 @@
 #include <linux/slab.h>
 #include <linux/version.h>
 #include <linux/vmalloc.h>
+#include <linux/wait.h>
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 20, 0)
 #define HAVE_XARRAY 1
 #include <linux/xarray.h>
@@ -847,6 +848,41 @@ static void drgn_test_idr_exit(void)
 	idr_destroy(&drgn_test_idr_sparse);
 }
 
+// wait-queue
+static struct task_struct *drgn_test_waitq_kthread;
+static wait_queue_head_t drgn_test_waitq;
+static wait_queue_head_t drgn_test_empty_waitq;
+static bool exit_waitq_test;
+
+static int drgn_test_waitq_kthread_fn(void *arg)
+{
+	wait_event_interruptible(drgn_test_waitq, exit_waitq_test);
+	return 0;
+}
+
+static int drgn_test_waitq_init(void)
+{
+	init_waitqueue_head(&drgn_test_waitq);
+	init_waitqueue_head(&drgn_test_empty_waitq);
+
+	drgn_test_waitq_kthread = kthread_create(drgn_test_waitq_kthread_fn, NULL,
+					   "drgn_test_waitq_kthread");
+	if (!drgn_test_waitq_kthread)
+		return -1;
+
+	wake_up_process(drgn_test_waitq_kthread);
+	return 0;
+}
+
+static void drgn_test_waitq_exit(void)
+{
+	if (drgn_test_waitq_kthread) {
+		exit_waitq_test = true;
+		kthread_stop(drgn_test_waitq_kthread);
+		drgn_test_waitq_kthread = NULL;
+	}
+}
+
 // Dummy function symbol.
 int drgn_test_function(int x)
 {
@@ -862,6 +898,7 @@ static void drgn_test_exit(void)
 	drgn_test_stack_trace_exit();
 	drgn_test_radix_tree_exit();
 	drgn_test_xarray_exit();
+	drgn_test_waitq_exit();
 	drgn_test_idr_exit();
 }
 
@@ -891,6 +928,10 @@ static int __init drgn_test_init(void)
 	if (ret)
 		goto out;
 	ret = drgn_test_xarray_init();
+	if (ret)
+		goto out;
+
+	ret = drgn_test_waitq_init();
 	if (ret)
 		goto out;
 	ret = drgn_test_idr_init();