1 files changed, 31 insertions, 5 deletions

diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
index bd7581b3a48a..99188c92068b 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:
@@ -340,6 +350,22 @@ static void serial_close(struct tty_struct *tty, struct file *filp)
 
         dbg("%s - port %d", __func__, port->number);
 
+        /* FIXME:
+           This leaves a very narrow race. Really we should do the
+           serial_do_free() on tty->shutdown(), but tty->shutdown can
+           be called from IRQ context and serial_do_free can sleep.
+
+           The right fix is probably to make the tty free (which is rare)
+           and thus tty->shutdown() occur via a work queue and simplify all
+           the drivers that use it.
+        */
+        if (tty_hung_up_p(filp)) {
+                /* serial_hangup already called serial_down at this point.
+                   Another user may have already reopened the port but
+                   serial_do_free is refcounted */
+                serial_do_free(port);
+                return;
+        }
 
         if (tty_port_close_start(&port->port, tty, filp) == 0)
                 return;
@@ -355,7 +381,8 @@ static void serial_hangup(struct tty_struct *tty)
         struct usb_serial_port *port = tty->driver_data;
         serial_do_down(port);
         tty_port_hangup(&port->port);
-        serial_do_free(port);
+        /* We must not free port yet - the USB serial layer depends on it's
+           continued existence */
 }
 
 static int serial_write(struct tty_struct *tty, const unsigned char *buf,
@@ -394,7 +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)