2019-06-10 07:56:31

by Jorge Ramirez-Ortiz

Subject: [PATCH v2] tty: serial: msm_serial: avoid system lockup condition

The function msm_wait_for_xmitr can be taken with interrupts
disabled. In order to avoid a potential system lockup - demonstrated
under stress testing conditions on SoC QCS404/5 - make sure we wait
for a bounded amount of time.

Tested on SoC QCS404.

Signed-off-by: Jorge Ramirez-Ortiz <[email protected]>
---
drivers/tty/serial/msm_serial.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index 23833ad952ba..3657a24913fc 100644
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -383,10 +383,14 @@ static void msm_request_rx_dma(struct msm_port *msm_port, resource_size_t base)

static inline void msm_wait_for_xmitr(struct uart_port *port)
{
+ unsigned int timeout = 500000;
+
while (!(msm_read(port, UART_SR) & UART_SR_TX_EMPTY)) {
if (msm_read(port, UART_ISR) & UART_ISR_TX_READY)
break;
udelay(1);
+ if (!timeout--)
+ break;
}
msm_write(port, UART_CR_CMD_RESET_TX_READY, UART_CR);
}
--
2.21.0

2019-06-10 17:06:32

by Greg Kroah-Hartman

Subject: Re: [PATCH v2] tty: serial: msm_serial: avoid system lockup condition

On Mon, Jun 10, 2019 at 09:55:54AM +0200, Jorge Ramirez-Ortiz wrote:
> The function msm_wait_for_xmitr can be taken with interrupts
> disabled. In order to avoid a potential system lockup - demonstrated
> under stress testing conditions on SoC QCS404/5 - make sure we wait
> for a bounded amount of time.
>
> Tested on SoC QCS404.
>
> Signed-off-by: Jorge Ramirez-Ortiz <[email protected]>
> ---
> drivers/tty/serial/msm_serial.c | 4 ++++
> 1 file changed, 4 insertions(+)

What changed from v1? Always put that below the --- line.

v3 please.

thanks,

greg k-h