The -rt patch triggers a lockdep warning for serial drivers if
tty_flip_buffer_push() is called with uart_port->lock locked. This never shows
up on UP kernels.
Release the port lock before calling tty_flip_buffer_push() and reacquire it
after the call.
Similar stuff was already done for few other drivers in the past, like:
commit 2389b272168ceec056ca1d8a870a97fa9c26e11a
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Date: Tue May 29 21:53:50 2007 +0100
[ARM] 4417/1: Serial: Fix AMBA drivers locking
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
drivers/tty/serial/mfd.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/drivers/tty/serial/mfd.c b/drivers/tty/serial/mfd.c
index 4a82267..d3db042 100644
--- a/drivers/tty/serial/mfd.c
+++ b/drivers/tty/serial/mfd.c
@@ -386,7 +386,7 @@ static void serial_hsu_stop_tx(struct uart_port *port)
/* This is always called in spinlock protected mode, so
* modify timeout timer is safe here */
-void hsu_dma_rx(struct uart_hsu_port *up, u32 int_sts)
+void hsu_dma_rx(struct uart_hsu_port *up, u32 int_sts, unsigned long *flags)
{
struct hsu_dma_buffer *dbuf = &up->rxbuf;
struct hsu_dma_chan *chan = up->rxc;
@@ -438,7 +438,9 @@ void hsu_dma_rx(struct uart_hsu_port *up, u32 int_sts)
| (0x1 << 16)
| (0x1 << 24) /* timeout bit, see HSU Errata 1 */
);
+ spin_unlock_irqrestore(&up->port.lock, *flags);
tty_flip_buffer_push(tport);
+ spin_lock_irqsave(&up->port.lock, *flags);
chan_writel(chan, HSU_CH_CR, 0x3);
@@ -459,7 +461,8 @@ static void serial_hsu_stop_rx(struct uart_port *port)
}
}
-static inline void receive_chars(struct uart_hsu_port *up, int *status)
+static inline void receive_chars(struct uart_hsu_port *up, int *status,
+ unsigned long *flags)
{
unsigned int ch, flag;
unsigned int max_count = 256;
@@ -519,7 +522,10 @@ static inline void receive_chars(struct uart_hsu_port *up, int *status)
ignore_char:
*status = serial_in(up, UART_LSR);
} while ((*status & UART_LSR_DR) && max_count--);
+
+ spin_unlock_irqrestore(&up->port.lock, *flags);
tty_flip_buffer_push(&up->port.state->port);
+ spin_lock_irqsave(&up->port.lock, *flags);
}
static void transmit_chars(struct uart_hsu_port *up)
@@ -613,7 +619,7 @@ static irqreturn_t port_irq(int irq, void *dev_id)
lsr = serial_in(up, UART_LSR);
if (lsr & UART_LSR_DR)
- receive_chars(up, &lsr);
+ receive_chars(up, &lsr, &flags);
check_modem_status(up);
/* lsr will be renewed during the receive_chars */
@@ -643,7 +649,7 @@ static inline void dma_chan_irq(struct hsu_dma_chan *chan)
/* Rx channel */
if (chan->dirt == DMA_FROM_DEVICE)
- hsu_dma_rx(up, int_sts);
+ hsu_dma_rx(up, int_sts, &flags);
/* Tx channel */
if (chan->dirt == DMA_TO_DEVICE) {
--
1.7.12.rc2.18.g61b472e
--
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