Re: [PATCH v2 5/5] staging: vc04_services: vchiq_core: Stop kthreads on shutdown

[Stefan Wahren <wahrenst@xxxxxxx>]

Hi Umang,

Am 21.03.24 um 14:07 schrieb Umang Jain:
> 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 on vchiq_shutdown().
>
> This also address the following TODO item:
>   * Fix kernel module support
>
> hence drop it from the TODO item list.
>
> Signed-off-by: Umang Jain <umang.jain@xxxxxxxxxxxxxxxx>
> Reviewed-by: Kieran Bingham <kieran.bingham@xxxxxxxxxxxxxxxx>
> ---
>   drivers/staging/vc04_services/interface/TODO           |  7 -------
>   .../vc04_services/interface/vchiq_arm/vchiq_arm.c      |  8 ++++++--
>   .../vc04_services/interface/vchiq_arm/vchiq_core.c     | 10 +++++++---
>   3 files changed, 13 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/staging/vc04_services/interface/TODO b/drivers/staging/vc04_services/interface/TODO
> index 05eb5140d096..57a2d6761f9b 100644
> --- a/drivers/staging/vc04_services/interface/TODO
> +++ b/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
> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> index ad506016fc93..1d21f9cfbfe5 100644
> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> @@ -726,8 +726,9 @@ void free_bulk_waiter(struct vchiq_instance *instance)
>
>   int vchiq_shutdown(struct vchiq_instance *instance)
>   {
> -	int status = 0;
>   	struct vchiq_state *state = instance->state;
> +	struct vchiq_arm_state *arm_state;
> +	int status = 0;
>
>   	if (mutex_lock_killable(&state->mutex))
>   		return -EAGAIN;
> @@ -739,6 +740,9 @@ int vchiq_shutdown(struct vchiq_instance *instance)
>
>   	dev_dbg(state->dev, "core: (%p): returning %d\n", instance, status);
>
> +	arm_state = vchiq_platform_get_arm_state(state);
> +	kthread_stop(arm_state->ka_thread);
> +
>   	free_bulk_waiter(instance);
>   	kfree(instance);
>
> @@ -1310,7 +1314,7 @@ 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)) {
> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c
> index 76c27778154a..953ccd87f425 100644
> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c
> @@ -1936,7 +1936,7 @@ slot_handler_func(void *v)
>
>   	DEBUG_INITIALISE(local);
>
> -	while (1) {
> +	while (!kthread_should_stop()) {
>   		DEBUG_COUNT(SLOT_HANDLER_COUNT);
>   		DEBUG_TRACE(SLOT_HANDLER_LINE);
>   		remote_event_wait(&state->trigger_event, &local->trigger);
> @@ -1978,7 +1978,7 @@ recycle_func(void *v)
>   	if (!found)
>   		return -ENOMEM;
>
> -	while (1) {
> +	while (!kthread_should_stop()) {
>   		remote_event_wait(&state->recycle_event, &local->recycle);
>
>   		process_free_queue(state, found, length);
> @@ -1997,7 +1997,7 @@ sync_func(void *v)
>   			state->remote->slot_sync);
>   	int svc_fourcc;
>
> -	while (1) {
> +	while (!kthread_should_stop()) {
>   		struct vchiq_service *service;
>   		int msgid, size;
>   		int type;
> @@ -2844,6 +2844,10 @@ vchiq_shutdown_internal(struct vchiq_state *state, struct vchiq_instance *instan
>   		(void)vchiq_remove_service(instance, service->handle);
>   		vchiq_service_put(service);
>   	}
> +
> +	kthread_stop(state->sync_thread);
> +	kthread_stop(state->recycle_thread);
> +	kthread_stop(state->slot_handler_thread);

i had a little bit time to look at the corrupt issue, i think this
caused by this change. This function is called by vchiq_shutdown which
is exported and used by VCHIQ user drivers like bcm2835-audio or
mmal-vchiq. So this is absolutely not the right place to stop the kernel
threads and the issue is not specific to the Raspberry Pi 3.

>   }
>
>   int