From: Peter Hurley <peter@hurleysoftware.com>
Date: Wed, 11 Mar 2015 13:19:16 +0000 (-0400)
Subject: serial: 8250_dw: Fix deadlock in LCR workaround
X-Git-Tag: omap-for-v4.2/o2_dc~275^2
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7fd6f640f2dd17dac6ddd6702c378cb0bb9cfa11;p=pandora-kernel.git

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>
---

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