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author | Peter Hurley <peter@hurleysoftware.com> | 2015-03-11 09:19:16 -0400 |
---|---|---|
committer | Sasha Levin <sasha.levin@oracle.com> | 2015-03-28 09:36:25 -0400 |
commit | de62b348272ac2c5464e1fe7b90e0c2b5949849a (patch) | |
tree | 9389a1ef900e2616179e44f451034af5a979fcbf /drivers/tty | |
parent | 78df56cca6dcf5f2d8c65b642a3bbf2b199c8e88 (diff) | |
download | lwn-de62b348272ac2c5464e1fe7b90e0c2b5949849a.tar.gz lwn-de62b348272ac2c5464e1fe7b90e0c2b5949849a.zip |
serial: 8250_dw: Fix deadlock in LCR workaround
[ Upstream commit 7fd6f640f2dd17dac6ddd6702c378cb0bb9cfa11 ]
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: Sasha Levin <sasha.levin@oracle.com>
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 beea6ca73ee5..a69e31e3410f 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -111,7 +111,10 @@ 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); + */ } } @@ -148,7 +151,10 @@ 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); + */ } } |