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| author | Liang Li <liang.li@windriver.com> | 2013-01-19 17:52:10 +0800 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2013-07-27 05:34:33 +0100 |
| commit | 790e332c473eded2396dcf7e2902cbe4429b6a80 (patch) | |
| tree | ff710918d210e3aca26da8f4f9fced7832e9381c | |
| parent | 2487f0db30527032c4d56fc2d0b1a240fe89fef8 (diff) | |
| download | lwn-790e332c473eded2396dcf7e2902cbe4429b6a80.tar.gz lwn-790e332c473eded2396dcf7e2902cbe4429b6a80.zip | |
pch_uart: fix a deadlock when pch_uart as console
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>
| -rw-r--r-- | drivers/tty/serial/pch_uart.c | 29 |
1 files changed, 22 insertions, 7 deletions
diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c index 8d70fbc03d12..c0b487284d9b 100644 --- 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 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) - dev_err(&priv->pdev->dev, "Framing Error\n"); + if (lsr & UART_LSR_FE) { + port->icount.frame++; + error_msg[i++] = " Framing Error\n"; + } - if (lsr & UART_LSR_PE) - dev_err(&priv->pdev->dev, "Parity Error\n"); + if (lsr & UART_LSR_PE) { + port->icount.parity++; + error_msg[i++] = " Parity Error\n"; + } - if (lsr & UART_LSR_OE) - dev_err(&priv->pdev->dev, "Overrun 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) |