[PATCH] Convert serial_core oopses to BUG_ON

[Russell King <rmk+lkml@arm.linux.org.uk>]

Hi,

With reference to these two bugs:

	http://bugzilla.kernel.org/show_bug.cgi?id=5958
	http://bugzilla.kernel.org/show_bug.cgi?id=6131

it seems that folk are under the impression that serial_core is
responsible for these bugs.  It isn't.

Calling serial functions to flush buffers, or try to send more data
after the port has been closed or hung up is a bug in the code doing
the calling, not in the serial_core driver.

Make this explicitly obvious by adding BUG_ON()'s.

I don't particularly want to add these BUG_ON()'s since they have a
performance impact, but it seems that they're necessary to convey
sufficient understanding about where the bug lies.  The Bluetooth
problem has been around for _ages_ (longer than the entry in bugzilla)
and no one seems the least bit interested in fixing the fscking thing.

I can only hope that adding these BUG_ON()'s provides sufficient
clarity to cause people to look elsewhere.

diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -71,6 +71,11 @@ static void uart_change_pm(struct uart_s
 void uart_write_wakeup(struct uart_port *port)
 {
 	struct uart_info *info = port->info;
+	/*
+	 * This means you called this function _after_ the port was
+	 * closed.  No cookie for you.
+	 */
+	BUG_ON(!info);
 	tasklet_schedule(&info->tlet);
 }
 
@@ -479,6 +484,12 @@ uart_write(struct tty_struct *tty, const
 	unsigned long flags;
 	int c, ret = 0;
 
+	/*
+	 * This means you called this function _after_ the port was
+	 * closed.  No cookie for you.
+	 */
+	BUG_ON(!state);
+
 	if (!circ->buf)
 		return 0;
 
@@ -521,6 +532,12 @@ static void uart_flush_buffer(struct tty
 	struct uart_port *port = state->port;
 	unsigned long flags;
 
+	/*
+	 * This means you called this function _after_ the port was
+	 * closed.  No cookie for you.
+	 */
+	BUG_ON(!state);
+
 	DPRINTK("uart_flush_buffer(%d) called\n", tty->index);
 
 	spin_lock_irqsave(&port->lock, flags);

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core
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