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

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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@gmail.com>
Cc: stable <stable@vger.kernel.org> # v3.12
[nicolas.ferre@atmel.com: modify commit message, call setup_timer() in any case]
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Marek Roszko 2014-01-10 10:33:11 +01:00 • committed by Greg Kroah-Hartman
parent 3685f19e07
commit 8bc661bfc0
1 changed files with 10 additions and 12 deletions
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22
drivers/tty/serial/atmel_serial.c
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@ -825,9 +825,6 @@ static void atmel_release_rx_dma(struct uart_port *port)
atmel_port->desc_rx = NULL; atmel_port->desc_rx = NULL;
atmel_port->chan_rx = NULL; atmel_port->chan_rx = NULL;
atmel_port->cookie_rx = -EINVAL; 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) 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); DMA_FROM_DEVICE);
kfree(pdc->buf); 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) 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 */ /* enable xmit & rcvr */
UART_PUT_CR(port, ATMEL_US_TXEN | ATMEL_US_RXEN); 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)) { if (atmel_use_pdc_rx(port)) {
/* set UART timeout */ /* set UART timeout */
if (!atmel_port->is_usart) { if (!atmel_port->is_usart) {
setup_timer(&atmel_port->uart_timer,
atmel_uart_timer_callback,
(unsigned long)port);
mod_timer(&atmel_port->uart_timer, mod_timer(&atmel_port->uart_timer,
jiffies + uart_poll_timeout(port)); jiffies + uart_poll_timeout(port));
/* set USART timeout */ /* set USART timeout */
@ -1624,9 +1619,6 @@ static int atmel_startup(struct uart_port *port)
} else if (atmel_use_dma_rx(port)) { } else if (atmel_use_dma_rx(port)) {
/* set UART timeout */ /* set UART timeout */
if (!atmel_port->is_usart) { if (!atmel_port->is_usart) {
setup_timer(&atmel_port->uart_timer,
atmel_uart_timer_callback,
(unsigned long)port);
mod_timer(&atmel_port->uart_timer, mod_timer(&atmel_port->uart_timer,
jiffies + uart_poll_timeout(port)); jiffies + uart_poll_timeout(port));
/* set USART timeout */ /* set USART timeout */
@ -1651,6 +1643,12 @@ static void atmel_shutdown(struct uart_port *port)
{ {
struct atmel_uart_port *atmel_port = to_atmel_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 * Clear out any scheduled tasklets before
* we destroy the buffers * we destroy the buffers