usb: typec: tcpm: fix tcpm unregister port but leave a pending timer

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: 3ed8e1c ("usb: typec: tcpm: Migrate workqueue to RT priority for processing events")
cc: <stable@vger.kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Link: https://lore.kernel.org/r/20211209101507.499096-1-xu.yang_2@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Xu Yang

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;
 
@@ -6291,31 +6292,35 @@ 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;
 }
 
 static enum hrtimer_restart vdm_state_machine_timer_handler(struct hrtimer *timer)
 {
 	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;
 }
 
 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;
 }
 
 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);