tty: tty_port: Change the buffer allocator locking

We want to be able to do this without regard for the activate/own open
method being used which causes a problem using port->mutex. Add another
mutex for now. Once everything uses port_open to do buffer allocs we can
kill it back off

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 6 insertions, 4 deletions

diff --git a/drivers/char/tty_port.c b/drivers/char/tty_port.c
index dd471d63fae2..3ef644a2e517 100644
--- a/drivers/char/tty_port.c
+++ b/drivers/char/tty_port.c
@@ -25,6 +25,7 @@ void tty_port_init(struct tty_port *port)
         init_waitqueue_head(&port->close_wait);
         init_waitqueue_head(&port->delta_msr_wait);
         mutex_init(&port->mutex);
+        mutex_init(&port->buf_mutex);
         spin_lock_init(&port->lock);
         port->close_delay = (50 * HZ) / 100;
         port->closing_wait = (3000 * HZ) / 100;
@@ -34,10 +35,10 @@ EXPORT_SYMBOL(tty_port_init);
 int tty_port_alloc_xmit_buf(struct tty_port *port)
 {
         /* We may sleep in get_zeroed_page() */
-        mutex_lock(&port->mutex);
+        mutex_lock(&port->buf_mutex);
         if (port->xmit_buf == NULL)
                 port->xmit_buf = (unsigned char *)get_zeroed_page(GFP_KERNEL);
-        mutex_unlock(&port->mutex);
+        mutex_unlock(&port->buf_mutex);
         if (port->xmit_buf == NULL)
                 return -ENOMEM;
         return 0;
@@ -46,12 +47,12 @@ EXPORT_SYMBOL(tty_port_alloc_xmit_buf);
 
 void tty_port_free_xmit_buf(struct tty_port *port)
 {
-        mutex_lock(&port->mutex);
+        mutex_lock(&port->buf_mutex);
         if (port->xmit_buf != NULL) {
                 free_page((unsigned long)port->xmit_buf);
                 port->xmit_buf = NULL;
         }
-        mutex_unlock(&port->mutex);
+        mutex_unlock(&port->buf_mutex);
 }
 EXPORT_SYMBOL(tty_port_free_xmit_buf);
 
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 6352ac257fcb..e9269ca1542a 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -212,6 +212,7 @@ struct tty_port {
         wait_queue_head_t       delta_msr_wait; /* Modem status change */
         unsigned long           flags;          /* TTY flags ASY_*/
         struct mutex            mutex;          /* Locking */
+        struct mutex            buf_mutex;      /* Buffer alloc lock */
         unsigned char           *xmit_buf;      /* Optional buffer */
         unsigned int            close_delay;    /* Close port delay */
         unsigned int            closing_wait;   /* Delay for output */