Hi heikki,
> -----Original Message-----
> From: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> Sent: Monday, October 11, 2021 2:31 PM
> To: Xu Yang <xu.yang_2@xxxxxxx>; linux@xxxxxxxxxxxx
> Cc: Jun Li <jun.li@xxxxxxx>; gregkh@xxxxxxxxxxxxxxxxxxx; linux-
> usb@xxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>
> Subject: [EXT] Re: [PATCH v2] usb: typec: tcpm: fix issue of multiple
> tcpm_set_state
>
> Caution: EXT Email
>
> Guenter, can you check this?
>
> On Fri, Aug 27, 2021 at 07:48:09PM +0800, Xu Yang wrote:
> > There are potential problems when states are set as following:
> >
> > tcpm_set_state(A, 0)
> > tcpm_set_state(B, X)
> >
> > As long as the state A is set and the state_machine work is queued
> > successfully, state_machine work will be scheduled soon after. Before
> > running into tcpm_state_machine_work(), there is a chance to set state
> > B again. If it does occur:
> >
> > either (X = 0)
> > port->state = B and state_machine work is queued again, then work
> > will be executed twice.
> > or (X != 0)
> > port->state = A and port->delayed_state = B, then work will be
> > executed once but timer is still running.
> >
> > For this situation, tcpm should only handle the most recent state
> > change as if only one state is set just now. Therefore, if the
> > state_machine work has already been queued, it can't be queued again
> > before running into tcpm_state_machine_work().
> >
> > The state_machine_running flag already prevents from queuing the work,
> > so we can make it contain the pending stage (after work be queued and
> > before running into tcpm_state_machine_work). The
> > state_machine_pending_or_running flag can be used to indicate that a
> > state can be handled without queuing the work again.
> >
> > Because the state_machine work has been queued for state A, there is
> > no way to cancel as it may be already dequeued later, and then will
> > run into
> > tcpm_state_machine_work() certainly. To handle the delayed state B,
> > such an abnormal work should be skiped. If port->delayed_state !=
> > INVALID_STATE and timer is still running, it's time to skip.
> >
> > Fixes: 4b4e02c83167 ("typec: tcpm: Move out of staging")
> > cc: <stable@xxxxxxxxxxxxxxx>
> > Signed-off-by: Xu Yang <xu.yang_2@xxxxxxx>
>
> What changed since v1?
>
> thanks,
In patch v1, I committed two patches to fix two problems. However, the two
problems are resulted by the same reason. And I try to address the issues
after it occurs.
In patch v2, according to Guenter's advice, I try to avoid such problems
occurring from the source. So I set a state_machine_pending_or_running flag
to indicate that a state can be handled without queuing the work again.
Meanwhile, one patch is enough to address the problems.
Xu Yang
>
> > diff --git a/drivers/usb/typec/tcpm/tcpm.c
> > b/drivers/usb/typec/tcpm/tcpm.c index 049f4c61ee82..a913bc620e88
> > 100644
> > --- a/drivers/usb/typec/tcpm/tcpm.c
> > +++ b/drivers/usb/typec/tcpm/tcpm.c
> > @@ -371,7 +371,7 @@ struct tcpm_port {
> > struct kthread_work enable_frs;
> > struct hrtimer send_discover_timer;
> > struct kthread_work send_discover_work;
> > - bool state_machine_running;
> > + bool state_machine_pending_or_running;
> > bool vdm_sm_running;
> >
> > struct completion tx_complete;
> > @@ -1192,6 +1192,7 @@ static void mod_tcpm_delayed_work(struct
> tcpm_port *port, unsigned int delay_ms)
> > } else {
> > hrtimer_cancel(&port->state_machine_timer);
> > kthread_queue_work(port->wq, &port->state_machine);
> > + port->state_machine_pending_or_running = true;
> > }
> > }
> >
> > @@ -1250,7 +1251,7 @@ static void tcpm_set_state(struct tcpm_port
> *port, enum tcpm_state state,
> > * tcpm_state_machine_work() will continue running the state
> > * machine.
> > */
> > - if (!port->state_machine_running)
> > + if (!port->state_machine_pending_or_running)
> > mod_tcpm_delayed_work(port, 0);
> > }
> > }
> > @@ -4810,13 +4811,15 @@ static void tcpm_state_machine_work(struct
> kthread_work *work)
> > enum tcpm_state prev_state;
> >
> > mutex_lock(&port->lock);
> > - port->state_machine_running = true;
> >
> > if (port->queued_message && tcpm_send_queued_message(port))
> > goto done;
> >
> > /* If we were queued due to a delayed state change, update it now */
> > if (port->delayed_state) {
> > + if (ktime_before(ktime_get(), port->delayed_runtime))
> > + goto done;
> > +
> > tcpm_log(port, "state change %s -> %s [delayed %ld ms]",
> > tcpm_states[port->state],
> > tcpm_states[port->delayed_state],
> > port->delay_ms); @@ -4837,7 +4840,7 @@ static void
> tcpm_state_machine_work(struct kthread_work *work)
> > } while (port->state != prev_state && !port->delayed_state);
> >
> > done:
> > - port->state_machine_running = false;
> > + port->state_machine_pending_or_running = false;
> > mutex_unlock(&port->lock);
> > }
> >
> > @@ -6300,6 +6303,7 @@ 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);
> > + port->state_machine_pending_or_running = true;
> > return HRTIMER_NORESTART;
> > }
> >
> > --
> > 2.25.1
>
> --
> heikki
