* [PATCH v2] PREEMPT_RT: USB serial gadget: Fix locking issue
@ 2014-05-22 9:58 Jean-Jacques Hiblot
2014-05-22 14:09 ` Felipe Balbi
0 siblings, 1 reply; 4+ messages in thread
From: Jean-Jacques Hiblot @ 2014-05-22 9:58 UTC (permalink / raw)
To: linux-kernel; +Cc: mingo, tglx, gregkh, balbi, Jean-Jacques Hiblot
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@traphandler.com>
---
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
+ /* 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
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2] PREEMPT_RT: USB serial gadget: Fix locking issue
2014-05-22 9:58 [PATCH v2] PREEMPT_RT: USB serial gadget: Fix locking issue Jean-Jacques Hiblot
@ 2014-05-22 14:09 ` Felipe Balbi
2014-05-22 14:57 ` [PATCH v2 RESEND] " Jean-Jacques Hiblot
0 siblings, 1 reply; 4+ messages in thread
From: Felipe Balbi @ 2014-05-22 14:09 UTC (permalink / raw)
To: Jean-Jacques Hiblot; +Cc: linux-kernel, mingo, tglx, gregkh, balbi
[-- Attachment #1: Type: text/plain, Size: 595 bytes --]
Hi,
On Thu, May 22, 2014 at 11:58:48AM +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@traphandler.com>
can you please resend with linux-usb in copy ?
--
balbi
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^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v2 RESEND] PREEMPT_RT: USB serial gadget: Fix locking issue
2014-05-22 14:09 ` Felipe Balbi
@ 2014-05-22 14:57 ` Jean-Jacques Hiblot
2014-06-19 15:10 ` Felipe Balbi
0 siblings, 1 reply; 4+ messages in thread
From: Jean-Jacques Hiblot @ 2014-05-22 14:57 UTC (permalink / raw)
To: linux-kernel; +Cc: linux-usb, mingo, tglx, gregkh, balbi, Jean-Jacques Hiblot
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@traphandler.com>
---
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
+ /* 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
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2 RESEND] PREEMPT_RT: USB serial gadget: Fix locking issue
2014-05-22 14:57 ` [PATCH v2 RESEND] " Jean-Jacques Hiblot
@ 2014-06-19 15:10 ` Felipe Balbi
0 siblings, 0 replies; 4+ messages in thread
From: Felipe Balbi @ 2014-06-19 15:10 UTC (permalink / raw)
To: Jean-Jacques Hiblot; +Cc: linux-kernel, linux-usb, mingo, tglx, gregkh, balbi
[-- Attachment #1: Type: text/plain, Size: 2115 bytes --]
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@traphandler.com>
> ---
> 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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^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2014-06-19 15:11 UTC | newest]
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2014-05-22 9:58 [PATCH v2] PREEMPT_RT: USB serial gadget: Fix locking issue Jean-Jacques Hiblot
2014-05-22 14:09 ` Felipe Balbi
2014-05-22 14:57 ` [PATCH v2 RESEND] " Jean-Jacques Hiblot
2014-06-19 15:10 ` Felipe Balbi
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