From: Eric W. Biederman <ebiederm@xmission.com>
Date: Wed, 6 Jan 2010 01:56:02 +0000 (-0800)
Subject: Input: serio - fix potential deadlock when unbinding drivers
X-Git-Tag: v2.6.33-rc5~65^2~10
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=59b015133cd0034f5904a76969d73476380aac46;p=pandora-kernel.git

Input: serio - fix potential deadlock when unbinding drivers

sysfs_remove_group() waits for sysfs attributes to be removed, therefore
we do not need to worry about driver-specific attributes being accessed
after driver has been detached from the device. In fact, attempts to take
serio->drv_mutex in attribute methods may lead to the following deadlock:

                                          sysfs_read_file()
                                            fill_read_buffer()
                                              sysfs_get_active_two()
                                                psmouse_attr_show_helper()
                                                  serio_pin_driver()
serio_disconnect_driver()
  mutex_lock(&serio->drv_mutex);
                                <-------->        mutex_lock(&serio_drv_mutex);
    psmouse_disconnect()
      sysfs_remove_group(... psmouse_attr_group);
        ....
        sysfs_deactivate();
          wait_for_completion();

Fix this by removing calls to serio_[un]pin_driver() and functions themselves
and using driver-private mutexes to serialize access to attribute's set()
methods that may change device state.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
---

Reading git-diff-tree failed