From 8bc661bfc0c2d221e209f4205bdaaf574d50100c Mon Sep 17 00:00:00 2001 From: Marek Roszko Date: Fri, 10 Jan 2014 10:33:11 +0100 Subject: [PATCH] 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 Cc: stable # v3.12 [nicolas.ferre@atmel.com: modify commit message, call setup_timer() in any case] Signed-off-by: Nicolas Ferre Signed-off-by: Greg Kroah-Hartman --- 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 2b6ac1b..a49f10d 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 */ -- 2.7.4