Re: [PATCH V2] usb: typec: tcpm: fix tcpm unregister port but leave a pending timer

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

On Thu, Dec 09, 2021 at 06:15:07PM +0800, Xu Yang wrote:
> In current design, when the tcpm port is unregisterd, the kthread_worker
> will be destroyed in the last step. Inside the kthread_destroy_worker(),
> the worker will flush all the works and wait for them to end. However, if
> one of the works calls hrtimer_start(), this hrtimer will be pending until
> timeout even though tcpm port is removed. Once the hrtimer timeout, many
> strange kernel dumps appear.
> 
> Thus, we can first complete kthread_destroy_worker(), then cancel all the
> hrtimers. This will guarantee that no hrtimer is pending at the end.
> 
> Fixes: 3ed8e1c2ac99 ("usb: typec: tcpm: Migrate workqueue to RT priority for processing events")
> cc: <stable@vger.kernel.org>
> Signed-off-by: Xu Yang <xu.yang_2@nxp.com>

Guenter should take a look at this.

Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
> Changes in V2:
>  -Introduced a flag "port->registered" to avoid race.
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index 6010b9901126..59d4fa2443f2 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -324,6 +324,7 @@ struct tcpm_port {
>  
>  	bool attached;
>  	bool connected;
> +	bool registered;
>  	bool pd_supported;
>  	enum typec_port_type port_type;
>  
> @@ -6291,7 +6292,8 @@ static enum hrtimer_restart state_machine_timer_handler(struct hrtimer *timer)
>  {
>  	struct tcpm_port *port = container_of(timer, struct tcpm_port, state_machine_timer);
>  
> -	kthread_queue_work(port->wq, &port->state_machine);
> +	if (port->registered)
> +		kthread_queue_work(port->wq, &port->state_machine);
>  	return HRTIMER_NORESTART;
>  }
>  
> @@ -6299,7 +6301,8 @@ static enum hrtimer_restart vdm_state_machine_timer_handler(struct hrtimer *time
>  {
>  	struct tcpm_port *port = container_of(timer, struct tcpm_port, vdm_state_machine_timer);
>  
> -	kthread_queue_work(port->wq, &port->vdm_state_machine);
> +	if (port->registered)
> +		kthread_queue_work(port->wq, &port->vdm_state_machine);
>  	return HRTIMER_NORESTART;
>  }
>  
> @@ -6307,7 +6310,8 @@ static enum hrtimer_restart enable_frs_timer_handler(struct hrtimer *timer)
>  {
>  	struct tcpm_port *port = container_of(timer, struct tcpm_port, enable_frs_timer);
>  
> -	kthread_queue_work(port->wq, &port->enable_frs);
> +	if (port->registered)
> +		kthread_queue_work(port->wq, &port->enable_frs);
>  	return HRTIMER_NORESTART;
>  }
>  
> @@ -6315,7 +6319,8 @@ static enum hrtimer_restart send_discover_timer_handler(struct hrtimer *timer)
>  {
>  	struct tcpm_port *port = container_of(timer, struct tcpm_port, send_discover_timer);
>  
> -	kthread_queue_work(port->wq, &port->send_discover_work);
> +	if (port->registered)
> +		kthread_queue_work(port->wq, &port->send_discover_work);
>  	return HRTIMER_NORESTART;
>  }
>  
> @@ -6403,6 +6408,7 @@ struct tcpm_port *tcpm_register_port(struct device *dev, struct tcpc_dev *tcpc)
>  	typec_port_register_altmodes(port->typec_port,
>  				     &tcpm_altmode_ops, port,
>  				     port->port_altmode, ALTMODE_DISCOVERY_MAX);
> +	port->registered = true;
>  
>  	mutex_lock(&port->lock);
>  	tcpm_init(port);
> @@ -6424,6 +6430,9 @@ void tcpm_unregister_port(struct tcpm_port *port)
>  {
>  	int i;
>  
> +	port->registered = false;
> +	kthread_destroy_worker(port->wq);
> +
>  	hrtimer_cancel(&port->send_discover_timer);
>  	hrtimer_cancel(&port->enable_frs_timer);
>  	hrtimer_cancel(&port->vdm_state_machine_timer);
> @@ -6435,7 +6444,6 @@ void tcpm_unregister_port(struct tcpm_port *port)
>  	typec_unregister_port(port->typec_port);
>  	usb_role_switch_put(port->role_sw);
>  	tcpm_debugfs_exit(port);
> -	kthread_destroy_worker(port->wq);
>  }
>  EXPORT_SYMBOL_GPL(tcpm_unregister_port);
>  
> -- 
> 2.25.1

-- 
heikki