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Commit 384e301e authored by Liang Li's avatar Liang Li Committed by Greg Kroah-Hartman
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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: default avatarLiang Li <liang.li@windriver.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 64325a3b

drivers/tty/serial/pch_uart.c

+22 −7
Original line number Diff line number Diff line
@@ -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)