On Thu, May 22, 2014 at 04:57:31PM +0200, Jean-Jacques Hiblot wrote:
> With CONFIG_PREEMPT_RT_FULL the tty_flip_buffer_push(..) actions are executed
> immeditely (same behaviour as if low_latency flag was set). We thus have to
> release port_lock before callng tty_flip_buffer_push().
>
> This issue resultst of commits:
> 44a0c019: USB: g_serial: don't set low_latency flag
> dc0cbd1b: serial: 8250: Call flush_to_ldisc when the irq is threaded
>
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@xxxxxxxxxxxxxxx>
> ---
> changes since v1:
> - fix compilation problem: use port.tty instead of port->port_tty
>
> drivers/usb/gadget/u_serial.c | 23 ++++++++++++++++++-----
> 1 file changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/usb/gadget/u_serial.c b/drivers/usb/gadget/u_serial.c
> index b369292..3d4246d 100644
> --- a/drivers/usb/gadget/u_serial.c
> +++ b/drivers/usb/gadget/u_serial.c
> @@ -549,12 +549,25 @@ static void gs_rx_push(unsigned long _port)
> port->read_started--;
> }
>
> - /* Push from tty to ldisc; without low_latency set this is handled by
> - * a workqueue, so we won't get callbacks and can hold port_lock
> - */
> - if (do_push)
> + /* Push from tty to ldisc */
> + if (do_push) {
> +#ifndef CONFIG_PREEMPT_RT_FULL
can we drop the ifdef somehow ? Are there no better options here ?
> + /* without low_latency set this is handled by a workqueue, so
> + * we won't get callbacks and can hold port_lock
> + */
> tty_flip_buffer_push(&port->port);
> -
> +#else
> + /* CONFIG_PREEMPT_RT_FULL makes this a synchronous action. and
> + * it may trigger synchronous callbacks to this driver. We need
> + * to release the lock.
> + */
> + spin_unlock_irq(&port->port_lock);
> + tty_flip_buffer_push(&port->port);
> + spin_lock_irq(&port->port_lock);
> + /* tty may have been closed */
> + tty = port->port.tty;
> +#endif
> + }
>
> /* We want our data queue to become empty ASAP, keeping data
> * in the tty and ldisc (not here). If we couldn't push any
> --
> 1.9.2
>
--
balbi
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