Patch "tty/serial: at91: disable uart timer at start of shutdown" has been added to the 3.13-stable tree

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



This is a note to let you know that I've just added the patch titled

    tty/serial: at91: disable uart timer at start of shutdown

to the 3.13-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tty-serial-at91-disable-uart-timer-at-start-of-shutdown.patch
and it can be found in the queue-3.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 8bc661bfc0c2d221e209f4205bdaaf574d50100c Mon Sep 17 00:00:00 2001
From: Marek Roszko <mark.roszko@xxxxxxxxx>
Date: Fri, 10 Jan 2014 10:33:11 +0100
Subject: tty/serial: at91: disable uart timer at start of shutdown

From: Marek Roszko <mark.roszko@xxxxxxxxx>

commit 8bc661bfc0c2d221e209f4205bdaaf574d50100c upstream.

The uart timer will schedule a tasklet when it fires. It is possible that it
can fire inside _shutdown before it is killed in the dma and pdc cleanup
routines. This causes a tasklet that exists after the port is shutdown, so when
the kernel finally executes it, it panics as the tty port is NULL.

This is a somewhat rare condition but its possible if a program keeps on
opening/closing the port. It has been observed in particular with systemd
boot messages that were causing a kernel panic because of this behavior.

Moving the timer deletion to the beginning of the function stops a tasklet from
being scheduled unexpectedly.

Signed-off-by: Marek Roszko <mark.roszko@xxxxxxxxx>
[nicolas.ferre@xxxxxxxxx: modify commit message, call setup_timer() in any case]
Signed-off-by: Nicolas Ferre <nicolas.ferre@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/tty/serial/atmel_serial.c |   22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -825,9 +825,6 @@ static void atmel_release_rx_dma(struct
 	atmel_port->desc_rx = NULL;
 	atmel_port->chan_rx = NULL;
 	atmel_port->cookie_rx = -EINVAL;
-
-	if (!atmel_port->is_usart)
-		del_timer_sync(&atmel_port->uart_timer);
 }
 
 static void atmel_rx_from_dma(struct uart_port *port)
@@ -1229,9 +1226,6 @@ static void atmel_release_rx_pdc(struct
 				 DMA_FROM_DEVICE);
 		kfree(pdc->buf);
 	}
-
-	if (!atmel_port->is_usart)
-		del_timer_sync(&atmel_port->uart_timer);
 }
 
 static void atmel_rx_from_pdc(struct uart_port *port)
@@ -1604,12 +1598,13 @@ static int atmel_startup(struct uart_por
 	/* enable xmit & rcvr */
 	UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN);
 
+	setup_timer(&atmel_port->uart_timer,
+			atmel_uart_timer_callback,
+			(unsigned long)port);
+
 	if (atmel_use_pdc_rx(port)) {
 		/* set UART timeout */
 		if (!atmel_port->is_usart) {
-			setup_timer(&atmel_port->uart_timer,
-					atmel_uart_timer_callback,
-					(unsigned long)port);
 			mod_timer(&atmel_port->uart_timer,
 					jiffies + uart_poll_timeout(port));
 		/* set USART timeout */
@@ -1624,9 +1619,6 @@ static int atmel_startup(struct uart_por
 	} else if (atmel_use_dma_rx(port)) {
 		/* set UART timeout */
 		if (!atmel_port->is_usart) {
-			setup_timer(&atmel_port->uart_timer,
-					atmel_uart_timer_callback,
-					(unsigned long)port);
 			mod_timer(&atmel_port->uart_timer,
 					jiffies + uart_poll_timeout(port));
 		/* set USART timeout */
@@ -1652,6 +1644,12 @@ static void atmel_shutdown(struct uart_p
 	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 
 	/*
+	 * Prevent any tasklets being scheduled during
+	 * cleanup
+	 */
+	del_timer_sync(&atmel_port->uart_timer);
+
+	/*
 	 * Clear out any scheduled tasklets before
 	 * we destroy the buffers
 	 */


Patches currently in stable-queue which might be from mark.roszko@xxxxxxxxx are

queue-3.13/tty-serial-at91-disable-uart-timer-at-start-of-shutdown.patch
queue-3.13/tty-serial-at91-fix-race-condition-in-atmel_serial_remove.patch
queue-3.13/tty-serial-at91-handle-shutdown-more-safely.patch
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux Kernel]     [Kernel Development Newbies]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite Hiking]     [Linux Kernel]     [Linux SCSI]