staging: vc04_services: vchiq_core: Stop kthreads on vchiq module unload

The various kthreads thread functions (slot_handler_func, sync_func,
recycle_func) in vchiq_core and vchiq_keepalive_thread_func in
vchiq_arm should be stopped when the module is unloaded.

Previous attempt were made to address this but later reverted [1]
due to VC04 firmware corruption. The issue around
wait_event_interruptible() handling on stopping a kthread has been
handled in the previous commit. Hence, it is now safe to stop kthreads
on module unload, without any firmware corruption.

This also completes the "Fix kernel module support" TODO item, hence
drop it from the list.

[1] commit ebee9ca2 ("Revert "staging: vc04_services: vchiq_core: Stop kthreads on shutdown"")
Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
Tested-by: Stefan Wahren <wahrenst@gmx.net>
Link: https://lore.kernel.org/r/20240703131052.597443-3-umang.jain@ideasonboard.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/interface/TODO

@@ -16,13 +16,6 @@ some of the ones we want:
   to manage these buffers as dmabufs so that we can zero-copy import
   camera images into vc4 for rendering/display.
 
-* Fix kernel module support
-
-Even the VPU firmware doesn't support a VCHI re-connect, the driver
-should properly handle a module unload. This also includes that all
-resources must be freed (kthreads, debugfs entries, ...) and global
-variables avoided.
-
 * Documentation
 
 A short top-down description of this driver's architecture (function of

drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c

@@ -1315,7 +1315,7 @@ vchiq_keepalive_thread_func(void *v)
 		goto shutdown;
 	}
 
-	while (1) {
+	while (!kthread_should_stop()) {
 		long rc = 0, uc = 0;
 
 		if (wait_for_completion_interruptible(&arm_state->ka_evt)) {
@@ -1776,12 +1776,20 @@ static int vchiq_probe(struct platform_device *pdev)
 static void vchiq_remove(struct platform_device *pdev)
 {
 	struct vchiq_drv_mgmt *mgmt = dev_get_drvdata(&pdev->dev);
+	struct vchiq_arm_state *arm_state;
 
 	vchiq_device_unregister(bcm2835_audio);
 	vchiq_device_unregister(bcm2835_camera);
 	vchiq_debugfs_deinit();
 	vchiq_deregister_chrdev();
 
+	kthread_stop(mgmt->state.sync_thread);
+	kthread_stop(mgmt->state.recycle_thread);
+	kthread_stop(mgmt->state.slot_handler_thread);
+
+	arm_state = vchiq_platform_get_arm_state(&mgmt->state);
+	kthread_stop(arm_state->ka_thread);
+
 	kfree(mgmt);
 }
 

drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c

@@ -1941,7 +1941,7 @@ slot_handler_func(void *v)
 
 	DEBUG_INITIALISE(local);
 
-	while (1) {
+	while (!kthread_should_stop()) {
 		DEBUG_COUNT(SLOT_HANDLER_COUNT);
 		DEBUG_TRACE(SLOT_HANDLER_LINE);
 		ret = remote_event_wait(&state->trigger_event, &local->trigger);
@@ -1986,7 +1986,7 @@ recycle_func(void *v)
 	if (!found)
 		return -ENOMEM;
 
-	while (1) {
+	while (!kthread_should_stop()) {
 		ret = remote_event_wait(&state->recycle_event, &local->recycle);
 		if (ret)
 			return ret;
@@ -2008,7 +2008,7 @@ sync_func(void *v)
 	int svc_fourcc;
 	int ret;
 
-	while (1) {
+	while (!kthread_should_stop()) {
 		struct vchiq_service *service;
 		int msgid, size;
 		int type;