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authorPeter Hurley <peter@hurleysoftware.com>2015-03-11 09:19:16 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-03-11 16:39:52 +0100
commit7fd6f640f2dd17dac6ddd6702c378cb0bb9cfa11 (patch)
treeb726c53178d24d15377206bcf25362d908b1420e /drivers/tty
parent9eccca0843205f87c00404b663188b88eb248051 (diff)
downloadop-kernel-dev-7fd6f640f2dd17dac6ddd6702c378cb0bb9cfa11.zip
op-kernel-dev-7fd6f640f2dd17dac6ddd6702c378cb0bb9cfa11.tar.gz
serial: 8250_dw: Fix deadlock in LCR workaround
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>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/serial/8250/8250_dw.c15
1 files changed, 12 insertions, 3 deletions
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 2ab229d..6ae5b85 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -119,7 +119,10 @@ 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);
+ */
}
}
@@ -163,7 +166,10 @@ static void dw8250_serial_outq(struct uart_port *p, int offset, int value)
__raw_writeq(value & 0xff,
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);
+ */
}
}
#endif /* CONFIG_64BIT */
@@ -187,7 +193,10 @@ 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);
+ */
}
}
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