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 my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-next branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will also be merged in the next major kernel release
during the merge window.
If you have any questions about this process, please let me know.
>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
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>
Cc: stable <stable@xxxxxxxxxxxxxxx> # v3.12
[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>
---
drivers/tty/serial/atmel_serial.c | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)
diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 2b6ac1be00d3..a49f10d269b2 100644
--- 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 uart_port *port)
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 uart_port *port)
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_port *port)
/* 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_port *port)
} 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_port *port)
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
*/
--
1.8.5.1.163.gd7aced9
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