于 2014年05月09日 23:19, dean_jenkins@xxxxxxxxxx 写道:
From: Andy Lowe<andy_lowe@xxxxxxxxxx>
The following deadlock has been observed:
imx_int() {
imx_txint() {
spin_lock_irqsave(&sport->port.lock,flags);
/* ^^^uart_port spinlock taken in imx_txint */
imx_transmit_buffer() {
uart_write_wakeup(&sport->port) {
tty_wakeup() {
hci_uart_tty_wakeup() {
hci_uart_tx_wakeup() {
uart_write() {
spin_lock_irqsave(&port->lock, flags);
/* ^^^deadlock here when spinlock is taken again */
.
.
.
spin_unlock_irqrestore(&port->lock, flags);
}
}
}
}
}
}
spin_unlock_irqrestore(&sport->port.lock,flags);
}
}
To correct this call uart_write_wakeup() at the end of imx_txint() after
the uart_port spinlock is unlocked.
Signed-off-by: Andy Lowe<andy_lowe@xxxxxxxxxx>
Signed-off-by: Dirk Behme<dirk.behme@xxxxxxxxxxxx>
---
drivers/tty/serial/imx.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index abe31ad..cc79706 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -636,8 +636,13 @@ static irqreturn_t imx_txint(int irq, void *dev_id)
imx_transmit_buffer(sport);
- if (uart_circ_chars_pending(xmit)< WAKEUP_CHARS)
+ if (uart_circ_chars_pending(xmit)< WAKEUP_CHARS) {
+ spin_unlock_irqrestore(&sport->port.lock, flags);
uart_write_wakeup(&sport->port);
+ } else
+ spin_unlock_irqrestore(&sport->port.lock, flags);
+
+ return IRQ_HANDLED;
out:
spin_unlock_irqrestore(&sport->port.lock, flags);
I think this patch :
https://lkml.org/lkml/2014/3/20/623
has fixed this deadlock.
We can ignore this patch now.
thanks
Huang Shijie
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