diff options
| author | Peter Hurley <peter@hurleysoftware.com> | 2015-03-11 09:19:16 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-04-29 10:33:57 +0200 |
| commit | e3f5ff371c1e9ad273f403c6a487f972bc5bd058 (patch) | |
| tree | dd1dc22decda0b856c4e9c0621064e8a589d92c9 | |
| parent | 57a99bf7d2f467714ba9db090a2f700cb080e0d9 (diff) | |
serial: 8250_dw: Fix deadlock in LCR workaround
commit 7fd6f640f2dd17dac6ddd6702c378cb0bb9cfa11 upstream.
Trying to write console output from within the serial console driver
while the port->lock is held causes recursive deadlock:
CPU 0
spin_lock_irqsave(&port->lock)
printk()
console_unlock()
call_console_drivers()
serial8250_console_write()
spin_lock_irqsave(&port->lock)
** DEADLOCK **
The 8250_dw i/o accessors try to write a console error message if the
LCR workaround was unsuccessful. When the port->lock is already held
(eg., when called from serial8250_set_termios()), this deadlocks.
Make the error message a FIXME until a general solution is devised.
Cc: Tim Kryger <tim.kryger@gmail.com>
Reported-by: Zhang Zhen <zhenzhang.zhang@huawei.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/serial/8250/8250_dw.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c index 345b5ddcb1a0..86281fa5dcc3 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -98,7 +98,10 @@ static void dw8250_serial_out(struct uart_port *p, int offset, int value) dw8250_force_idle(p); writeb(value, p->membase + (UART_LCR << p->regshift)); } - dev_err(p->dev, "Couldn't set LCR to %d\n", value); + /* + * FIXME: this deadlocks if port->lock is already held + * dev_err(p->dev, "Couldn't set LCR to %d\n", value); + */ } } @@ -128,7 +131,10 @@ static void dw8250_serial_out32(struct uart_port *p, int offset, int value) dw8250_force_idle(p); writel(value, p->membase + (UART_LCR << p->regshift)); } - dev_err(p->dev, "Couldn't set LCR to %d\n", value); + /* + * FIXME: this deadlocks if port->lock is already held + * dev_err(p->dev, "Couldn't set LCR to %d\n", value); + */ } } |