pch_uart: fix a deadlock when pch_uart as console

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>

diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
index 8b40a1fc9681410dc89371e703d45906f0236d1e..10e1a95b0c92c6256b12c21a0d821a9a36cb2ed7 100644 (file)
--- a/drivers/tty/serial/pch_uart.c
+++ b/drivers/tty/serial/pch_uart.c
@@ -1024,22 +1024,37 @@ static unsigned int dma_handle_tx(struct eg20t_port *priv)
 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) {
+               port->icount.frame++;
+               error_msg[i++] = "  Framing Error\n";
+       }
 
-       if (lsr & UART_LSR_FE)
-               dev_err(&priv->pdev->dev, "Framing Error\n");
+       if (lsr & UART_LSR_PE) {
+               port->icount.parity++;
+               error_msg[i++] = "  Parity Error\n";
+       }
 
-       if (lsr & UART_LSR_PE)
-               dev_err(&priv->pdev->dev, "Parity Error\n");
+       if (lsr & UART_LSR_OE) {
+               port->icount.overrun++;
+               error_msg[i++] = "  Overrun Error\n";
+       }
 
-       if (lsr & UART_LSR_OE)
-               dev_err(&priv->pdev->dev, "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)