On Wed, Aug 22, 2012 at 10:50:35PM +0300, Timo Kokkonen wrote:
> The lirc-dev expects the ir-code to be transmitted when the write call
> returns back to the user space. We should not leave TX ongoing no
> matter what is the reason we return to the user space. Easiest
> solution for that is to simply remove interruptible sleeps.
>
> The first wait_event_interruptible is thus replaced with return -EBUSY
> in case there is still ongoing transfer. This should suffice as the
> concept of sending multiple codes in parallel does not make sense.
>
> The second wait_event_interruptible call is replaced with
> wait_even_timeout with a fixed and safe timeout that should prevent
> the process from getting stuck in kernel for too long.
>
> Also, from now on we will force the TX to stop before we return from
> write call. If the TX happened to time out for some reason, we should
> not leave the HW transmitting anything.
>
> Signed-off-by: Timo Kokkonen <timo.t.kokko...@iki.fi>
> ---
> drivers/media/rc/ir-rx51.c | 39 ++++++++++++++++++++++++++++-----------
> 1 file changed, 28 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/media/rc/ir-rx51.c b/drivers/media/rc/ir-rx51.c
> index 9487dd3..a7b787a 100644
> --- a/drivers/media/rc/ir-rx51.c
> +++ b/drivers/media/rc/ir-rx51.c
> @@ -74,6 +74,19 @@ static void lirc_rx51_off(struct lirc_rx51 *lirc_rx51)
> OMAP_TIMER_TRIGGER_NONE);
> }
>
> +static void lirc_rx51_stop_tx(struct lirc_rx51 *lirc_rx51)
> +{
> + if (lirc_rx51->wbuf_index < 0)
> + return;
> +
> + lirc_rx51_off(lirc_rx51);
> + lirc_rx51->wbuf_index = -1;
> + omap_dm_timer_stop(lirc_rx51->pwm_timer);
> + omap_dm_timer_stop(lirc_rx51->pulse_timer);
> + omap_dm_timer_set_int_enable(lirc_rx51->pulse_timer, 0);
> + wake_up_interruptible(&lirc_rx51->wqueue);
Unless I'm mistaken, wait_up_interruptable() won't wake up any
non-interruptable sleepers. Should this not be wake_up()?
> +}
> +
> static int init_timing_params(struct lirc_rx51 *lirc_rx51)
> {
> u32 load, match;
> @@ -160,13 +173,7 @@ static irqreturn_t lirc_rx51_interrupt_handler(int irq,
> void *ptr)
>
> return IRQ_HANDLED;
> end:
> - /* Stop TX here */
> - lirc_rx51_off(lirc_rx51);
> - lirc_rx51->wbuf_index = -1;
> - omap_dm_timer_stop(lirc_rx51->pwm_timer);
> - omap_dm_timer_stop(lirc_rx51->pulse_timer);
> - omap_dm_timer_set_int_enable(lirc_rx51->pulse_timer, 0);
> - wake_up_interruptible(&lirc_rx51->wqueue);
> + lirc_rx51_stop_tx(lirc_rx51);
>
> return IRQ_HANDLED;
> }
> @@ -246,8 +253,9 @@ static ssize_t lirc_rx51_write(struct file *file, const
> char *buf,
> if ((count > WBUF_LEN) || (count % 2 == 0))
> return -EINVAL;
>
> - /* Wait any pending transfers to finish */
> - wait_event_interruptible(lirc_rx51->wqueue, lirc_rx51->wbuf_index < 0);
> + /* We can have only one transmit at a time */
> + if (lirc_rx51->wbuf_index >= 0)
> + return -EBUSY;
>
> if (copy_from_user(lirc_rx51->wbuf, buf, n))
> return -EFAULT;
> @@ -273,9 +281,18 @@ static ssize_t lirc_rx51_write(struct file *file, const
> char *buf,
>
> /*
> * Don't return back to the userspace until the transfer has
> - * finished
> + * finished. However, we wish to not spend any more than 500ms
> + * in kernel. No IR code TX should ever take that long.
> + */
> + i = wait_event_timeout(lirc_rx51->wqueue, lirc_rx51->wbuf_index < 0,
Note non-interruptable sleeper.
> + HZ / 2);
> +
> + /*
> + * Ensure transmitting has really stopped, even if the timers
> + * went mad or something else happened that caused it still
> + * sending out something.
> */
> - wait_event_interruptible(lirc_rx51->wqueue, lirc_rx51->wbuf_index < 0);
> + lirc_rx51_stop_tx(lirc_rx51);
>
> /* We can sleep again */
> lirc_rx51->pdata->set_max_mpu_wakeup_lat(lirc_rx51->dev, -1);
> --
> 1.7.12
>
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