fix wait_queue rmmod deadlock, wait_queue2, add insrm.sh that was used to test wait_queue lock, which obsoletes workqueue_cheat.sh

kernel_module/wait_queue.c

@@ -39,8 +39,6 @@ static int kthread_func1(void *data)
 		wake_up(&queue);
 		i++;
 	}
-	i = !i;
-	wake_up_interruptible(&queue);
 	return 0;
 }
 
@@ -50,7 +48,7 @@ static int kthread_func2(void *data)
 	while (!kthread_should_stop()) {
 		pr_info("2 %u\n", i);
 		i++;
-		wait_event_interruptible(queue, atomic_read(&awake));
+		wait_event(queue, atomic_read(&awake));
 		atomic_set(&awake, 0);
 		schedule();
 	}
@@ -69,8 +67,9 @@ static int myinit(void)
 
 static void myexit(void)
 {
-	kthread_stop(kthread1);
+	/* 2 must be stopped before, or else we can deadlock. */
 	kthread_stop(kthread2);
+	kthread_stop(kthread1);
 }
 
 module_init(myinit)

kernel_module/wait_queue2.c

@@ -28,8 +28,6 @@ static int kthread_wake_func(void *data)
 		wake_up(&queue);
 		i++;
 	}
-	i = !i;
-	wake_up_interruptible(&queue);
 	return 0;
 }
 
@@ -73,7 +71,7 @@ int init_module(void)
 
 void cleanup_module(void)
 {
-	kthread_stop(kthread_wake);
-	kthread_stop(kthread_sleep1);
 	kthread_stop(kthread_sleep2);
+	kthread_stop(kthread_sleep1);
+	kthread_stop(kthread_wake);
 }

rootfs_overlay/insrm.sh

@@ -0,0 +1,13 @@
+#!/bin/sh
+# Insert and remove a module n times to check for spurious errors / deadlocks.
+set -e
+mod="$1"
+n="${2:-1}"
+i=0
+while [ $i -lt $n ]; do
+  echo "insmod $i"
+  insmod "/$mod.ko"
+  echo "rmmod $i"
+  rmmod "$mod"
+  i=$(($i+1))
+done

rootfs_overlay/workqueue_cheat.sh

@@ -1,9 +0,0 @@
-#!/bin/sh
-
-# Got a few kernel crashes after insert / remove, so let's do this a few times.
-insmod /workqueue_cheat.ko
-rmmod workqueue_cheat
-insmod /workqueue_cheat.ko
-rmmod workqueue_cheat
-insmod /workqueue_cheat.ko
-rmmod workqueue_cheat