On Tue 28.Jul'09 at 0:31:20 +0100, Alan Cox wrote:
> commit 3f40612e940971ecec29d5375cdcc9f9c9a9f46e
> Author: Alan Cox <alan@xxxxxxxxxxxxxxx>
> Date: Tue Jul 28 00:23:39 2009 +0100
>
> tty: USB lock/refcounting fixes
>
> This fixes
> - locking bug that was hidden by ecc2e05e739c30870c8e4f252b63a0c4041f2724
> - Regression #13821
> - Spurious warning when closing and blocking for data write out
>
> With these changes my PL2303 always ends up as ttyUSB0 when it should and
> the module refcounts stay correct.
>
> I'll do a more wholesale split & tidy of _open in the next release or two
> as we get a standard tty_port_open and port->ops->init port->ops->shutdown
> call backs.
>
> Signed-off-by: Alan Cox <alan@xxxxxxxxxxxxxxx>
I tested the patch below and it fixed the issue completely!
Thanks for your time Alan, I appreciate your work!
>
> diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
> index 3c8923f..99188c9 100644
> --- a/drivers/usb/serial/usb-serial.c
> +++ b/drivers/usb/serial/usb-serial.c
> @@ -32,6 +32,7 @@
> #include <linux/mutex.h>
> #include <linux/list.h>
> #include <linux/uaccess.h>
> +#include <linux/serial.h>
> #include <linux/usb.h>
> #include <linux/usb/serial.h>
> #include "pl2303.h"
> @@ -184,6 +185,7 @@ static int serial_open (struct tty_struct *tty, struct file *filp)
> struct usb_serial_port *port;
> unsigned int portNumber;
> int retval = 0;
> + int first = 0;
>
> dbg("%s", __func__);
>
> @@ -223,7 +225,7 @@ static int serial_open (struct tty_struct *tty, struct file *filp)
>
> /* If the console is attached, the device is already open */
> if (port->port.count == 1 && !port->console) {
> -
> + first = 1;
> /* lock this module before we call it
> * this may fail, which means we must bail out,
> * safe because we are called with BKL held */
> @@ -246,13 +248,21 @@ static int serial_open (struct tty_struct *tty, struct file *filp)
> if (retval)
> goto bailout_interface_put;
> mutex_unlock(&serial->disc_mutex);
> + set_bit(ASYNCB_INITIALIZED, &port->port.flags);
> }
> mutex_unlock(&port->mutex);
> /* Now do the correct tty layer semantics */
> retval = tty_port_block_til_ready(&port->port, tty, filp);
> - if (retval == 0)
> + if (retval == 0) {
> + if (!first)
> + usb_serial_put(serial);
> return 0;
> -
> + }
> + mutex_lock(&port->mutex);
> + if (first == 0)
> + goto bailout_mutex_unlock;
> + /* Undo the initial port actions */
> + mutex_lock(&serial->disc_mutex);
> bailout_interface_put:
> usb_autopm_put_interface(serial->interface);
> bailout_module_put:
> @@ -411,7 +421,6 @@ static int serial_chars_in_buffer(struct tty_struct *tty)
> struct usb_serial_port *port = tty->driver_data;
> dbg("%s = port %d", __func__, port->number);
>
> - WARN_ON(!port->port.count);
> /* if the device was unplugged then any remaining characters
> fell out of the connector ;) */
> if (port->serial->disconnected)
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