diff options
| author | Peter Hurley <peter@hurleysoftware.com> | 2015-03-11 09:19:16 -0400 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2015-11-14 18:58:27 +0100 |
| commit | 9bc623ed14f83e2facf5ada94405d39c2a7be3fd (patch) | |
| tree | fea7342900504f63b901bb9197d7eac91f4fcbd7 /drivers/tty | |
| parent | 30dd76cda0dccffcfa12f66913c6fe8b1b8ef396 (diff) | |
| download | lwn-9bc623ed14f83e2facf5ada94405d39c2a7be3fd.tar.gz lwn-9bc623ed14f83e2facf5ada94405d39c2a7be3fd.zip | |
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>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Diffstat (limited to 'drivers/tty')
| -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 70ecf541b77a..1831a138480c 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -101,7 +101,10 @@ 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); + */ } } @@ -138,7 +141,10 @@ 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); + */ } } |