pch_uart_interrupt() takes priv->port.lock which leads to two recursive
spinlock calls if low_latency==1 or CONFIG_PREEMPT_RT_FULL=y (one
otherwise):
pch_uart_interrupt
spin_lock_irqsave(priv->port.lock, flags)
case PCH_UART_IID_RDR_TO (data ready)
handle_rx_to
push_rx
tty_port_tty_get
spin_lock_irqsave(&port->lock, flags) <--- already hold this lock
...
tty_flip_buffer_push
...
flush_to_ldisc
spin_lock_irqsave(&tty->buf.lock)
spin_lock_irqsave(&tty->buf.lock)
disc->ops->receive_buf(tty, char_buf)
n_tty_receive_buf
tty->ops->flush_chars()
uart_flush_chars
uart_start
spin_lock_irqsave(&port->lock) <--- already hold this lock
Avoid this by using a dedicated lock to protect the eg20t_port structure
and IO access to its membase. This is more consistent with the 8250
driver. Ensure priv->lock is always take prior to priv->port.lock when
taken at the same time.
Signed-off-by: Darren Hart <dvh...@linux.intel.com>
CC: Tomoya MORINAGA <tomoya.r...@gmail.com>
CC: Feng Tang <feng.t...@intel.com>
CC: Alexander Stein <alexander.st...@systec-electronic.com>
CC: Greg Kroah-Hartman <gre...@linuxfoundation.org>
CC: Alan Cox <a...@linux.intel.com>
CC: linux-ser...@vger.kernel.org
---
drivers/tty/serial/pch_uart.c | 22 ++++++++++++++++------
1 files changed, 16 insertions(+), 6 deletions(-)
diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
index 565e099..db61d00 100644
--- a/drivers/tty/serial/pch_uart.c
+++ b/drivers/tty/serial/pch_uart.c
@@ -246,6 +246,8 @@ struct eg20t_port {
int tx_dma_use;
void *rx_buf_virt;
dma_addr_t rx_buf_dma;
+ /* protect the eg20t_port private structure and io access to membase */
+ spinlock_t lock;
};
/**
@@ -999,7 +1001,7 @@ static irqreturn_t pch_uart_interrupt(int irq, void
*dev_id)
unsigned int iid;
unsigned long flags;
- spin_lock_irqsave(&priv->port.lock, flags);
+ spin_lock_irqsave(&priv->lock, flags);
handled = 0;
while ((iid = pch_uart_hal_get_iid(priv)) > 1) {
switch (iid) {
@@ -1050,7 +1052,7 @@ static irqreturn_t pch_uart_interrupt(int irq, void
*dev_id)
priv->int_dis_flag = 0;
}
- spin_unlock_irqrestore(&priv->port.lock, flags);
+ spin_unlock_irqrestore(&priv->lock, flags);
return IRQ_RETVAL(handled);
}
@@ -1163,9 +1165,9 @@ static void pch_uart_break_ctl(struct uart_port *port,
int ctl)
unsigned long flags;
priv = container_of(port, struct eg20t_port, port);
- spin_lock_irqsave(&port->lock, flags);
+ spin_lock_irqsave(&priv->lock, flags);
pch_uart_hal_set_break(priv, ctl);
- spin_unlock_irqrestore(&port->lock, flags);
+ spin_unlock_irqrestore(&priv->lock, flags);
}
/* Grab any interrupt resources and initialise any low level driver state. */
@@ -1314,7 +1316,8 @@ static void pch_uart_set_termios(struct uart_port *port,
baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk / 16);
- spin_lock_irqsave(&port->lock, flags);
+ spin_lock_irqsave(&priv->lock, flags);
+ spin_lock(&port->lock);
uart_update_timeout(port, termios->c_cflag, baud);
rtn = pch_uart_hal_set_line(priv, baud, parity, bits, stb);
@@ -1327,7 +1330,8 @@ static void pch_uart_set_termios(struct uart_port *port,
tty_termios_encode_baud_rate(termios, baud, baud);
out:
- spin_unlock_irqrestore(&port->lock, flags);
+ spin_unlock(&port->lock);
+ spin_unlock_irqrestore(&priv->lock, flags);
}
static const char *pch_uart_type(struct uart_port *port)
@@ -1486,6 +1490,7 @@ pch_console_write(struct console *co, const char *s,
unsigned int count)
touch_nmi_watchdog();
local_irq_save(flags);
+ spin_lock(&priv->lock);
if (priv->port.sysrq) {
/* serial8250_handle_port() already took the lock */
locked = 0;
@@ -1494,6 +1499,7 @@ pch_console_write(struct console *co, const char *s,
unsigned int count)
} else
spin_lock(&priv->port.lock);
+
/*
* First save the IER then disable the interrupts
*/
@@ -1512,7 +1518,9 @@ pch_console_write(struct console *co, const char *s,
unsigned int count)
if (locked)
spin_unlock(&priv->port.lock);
+ spin_unlock(&priv->lock);
local_irq_restore(flags);
+
}
static int __init pch_console_setup(struct console *co, char *options)
@@ -1608,6 +1616,8 @@ static struct eg20t_port *pch_uart_init_port(struct
pci_dev *pdev,
pci_enable_msi(pdev);
pci_set_master(pdev);
+ spin_lock_init(&priv->lock);
+
iobase = pci_resource_start(pdev, 0);
mapbase = pci_resource_start(pdev, 1);
priv->mapbase = mapbase;
--
1.7.5.4
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