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SubjectRe: [PATCH] serial: fix possible imx deadlock
On Mon, Mar 15, 2010 at 10:08:58AM +0100, John Ogness wrote:
> This patch fixes a possible deadlock situation with the port and timer
> locks. The calling paths for the deadlock situation are:
>
> 1. imx_set_termios() -> LOCK(port.lock)
> -> del_timer_sync() -> LOCK(timer.base.lock)
>
> 2. run_timer_softirq() -> LOCK(timer.base.lock)
> -> imx_timeout() -> LOCK(port.lock)
>
> This patch is against 2.6.34-rc1.
>
> Signed-off-by: John Ogness <john.ogness@linutronix.de>
> ---
> drivers/serial/imx.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
> diff -Naurp a/drivers/serial/imx.c b/drivers/serial/imx.c
> --- a/drivers/serial/imx.c 2010-03-08 19:45:44.000000000 +0100
> +++ b/drivers/serial/imx.c 2010-03-15 09:52:39.855261060 +0100
> @@ -836,6 +836,12 @@ imx_set_termios(struct uart_port *port,
> baud = uart_get_baud_rate(port, termios, old, 50, port->uartclk / 16);
> quot = uart_get_divisor(port, baud);
>
> + /*
> + * Stop our timer. This is done with the port unlocked
> + * to avoid possible deadlock against the timer function.
> + */
> + del_timer_sync(&sport->timer);
> +

Is this call needed here anyway? Only few drivers have it. Does anyone
have more insights on this?

Sascha

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