lkml.org 
[lkml]   [2013]   [Jul]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Date
Subject[80/85] pch_uart: fix a deadlock when pch_uart as console
3.2.49-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Liang Li <liang.li@windriver.com>

commit 384e301e3519599b000c1a2ecd938b533fc15d85 upstream.

When we use pch_uart as system console like 'console=ttyPCH0,115200',
then 'send break' to it. We'll encounter the deadlock on a cpu/core,
with interrupts disabled on the core. When we happen to have all irqs
affinity to cpu0 then the deadlock on cpu0 actually deadlock whole
system.

In pch_uart_interrupt, we have spin_lock_irqsave(&priv->lock, flags)
then call pch_uart_err_ir when break is received. Then the call to
dev_err would actually call to pch_console_write then we'll run into
another spin_lock(&priv->lock), with interrupts disabled.

So in the call sequence lead by pch_uart_interrupt, we should be
carefully to call functions that will 'print message to console' only
in case the uart port is not being used as serial console.

Signed-off-by: Liang Li <liang.li@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/tty/serial/pch_uart.c | 29 ++++++++++++++++++++++-------
1 file changed, 22 insertions(+), 7 deletions(-)

--- a/drivers/tty/serial/pch_uart.c
+++ b/drivers/tty/serial/pch_uart.c
@@ -940,22 +940,37 @@ static unsigned int dma_handle_tx(struct
static void pch_uart_err_ir(struct eg20t_port *priv, unsigned int lsr)
{
u8 fcr = ioread8(priv->membase + UART_FCR);
+ struct uart_port *port = &priv->port;
+ struct tty_struct *tty = tty_port_tty_get(&port->state->port);
+ char *error_msg[5] = {};
+ int i = 0;

/* Reset FIFO */
fcr |= UART_FCR_CLEAR_RCVR;
iowrite8(fcr, priv->membase + UART_FCR);

if (lsr & PCH_UART_LSR_ERR)
- dev_err(&priv->pdev->dev, "Error data in FIFO\n");
+ error_msg[i++] = "Error data in FIFO\n";

- if (lsr & UART_LSR_FE)
- dev_err(&priv->pdev->dev, "Framing Error\n");
-
- if (lsr & UART_LSR_PE)
- dev_err(&priv->pdev->dev, "Parity Error\n");
-
- if (lsr & UART_LSR_OE)
- dev_err(&priv->pdev->dev, "Overrun Error\n");
+ if (lsr & UART_LSR_FE) {
+ port->icount.frame++;
+ error_msg[i++] = " Framing Error\n";
+ }
+
+ if (lsr & UART_LSR_PE) {
+ port->icount.parity++;
+ error_msg[i++] = " Parity Error\n";
+ }
+
+ if (lsr & UART_LSR_OE) {
+ port->icount.overrun++;
+ error_msg[i++] = " Overrun Error\n";
+ }
+
+ if (tty == NULL) {
+ for (i = 0; error_msg[i] != NULL; i++)
+ dev_err(&priv->pdev->dev, error_msg[i]);
+ }
}

static irqreturn_t pch_uart_interrupt(int irq, void *dev_id)


\
 
 \ /
  Last update: 2013-07-24 17:01    [W:0.440 / U:42.380 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site