On 09. 04. 24, 19:40, Andy Shevchenko wrote:
After conversion to the kfifo, it becomes possible to extract two helper
functions for better maintenance and code deduplication. Do it here.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
drivers/tty/serial/serial_core.c | 98 ++++++++++++++++++--------------
1 file changed, 54 insertions(+), 44 deletions(-)
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index dd6cf525d98d..ba2d6065fe02 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -243,25 +243,12 @@ static void uart_change_line_settings(struct tty_struct *tty, struct uart_state
uart_port_unlock_irq(uport);
}
-/*
- * Startup the port. This will be called once per open. All calls
- * will be serialised by the per-port mutex.
- */
-static int uart_port_startup(struct tty_struct *tty, struct uart_state *state,
- bool init_hw)
+static int uart_alloc_xmit_buf(struct tty_port *port)
{
- struct uart_port *uport = uart_port_check(state);
+ struct uart_state *state = container_of(port, struct uart_state, port);
+ struct uart_port *uport;
unsigned long flags;
unsigned long page;
- int retval = 0;
-
- if (uport->type == PORT_UNKNOWN)
- return 1;
-
- /*
- * Make sure the device is in D0 state.
- */
- uart_change_pm(state, UART_PM_STATE_ON);
/*
* Initialise and allocate the transmit and temporary
@@ -271,7 +258,7 @@ static int uart_port_startup(struct tty_struct *tty, struct uart_state *state,
if (!page)
return -ENOMEM;
- uart_port_lock(state, flags);
+ uport = uart_port_lock(state, flags);
if (!state->port.xmit_buf) {
state->port.xmit_buf = (unsigned char *)page;
kfifo_init(&state->port.xmit_fifo, state->port.xmit_buf,
@@ -281,11 +268,58 @@ static int uart_port_startup(struct tty_struct *tty, struct uart_state *state,
uart_port_unlock(uport, flags);
/*
* Do not free() the page under the port lock, see
- * uart_shutdown().
+ * uart_free_xmit_buf().
*/
free_page(page);
}
+ return 0;
+}
+
+static void uart_free_xmit_buf(struct tty_port *port)
+{
+ struct uart_state *state = container_of(port, struct uart_state, port);
+ struct uart_port *uport;
+ unsigned long flags;
+ char *xmit_buf;
+
+ /*
+ * Do not free() the transmit buffer page under the port lock since
+ * this can create various circular locking scenarios. For instance,
+ * console driver may need to allocate/free a debug object, which
+ * can end up in printk() recursion.
+ */
+ uport = uart_port_lock(state, flags);
+ xmit_buf = port->xmit_buf;
+ port->xmit_buf = NULL;
+ INIT_KFIFO(port->xmit_fifo);
+ uart_port_unlock(uport, flags);
+
+ free_page((unsigned long)xmit_buf);
+}
I see very much of tty_port_alloc_xmit_buf() and
tty_port_free_xmit_buf() in here :).
Currently, different locks are used, so the patch is, I think, good for
now. For future, we should switch to the tty port helpers.
Actually have you looked if the different locking is an issue at all?
IOW, isn't the tty_port's (and its xmit buf) lifetime enough w/o uart
port locks?
thanks,
--
js
suse labs
