A number of driver functions are so obviously trivial that they do not need
the big kernel lock - at least not overtly.  It turns out that the
acquisition of the BKL in driver open() functions can perform a sort of
poor-hacker's serialization function, delaying the open operation until the
driver is certain to have completed its initialization.  Add a simple
cycle_kernel_lock() function for these cases to make it clear that there is
no need to *hold* the BKL, just to be sure that we can acquire it.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Put explicit lock_kernel() calls into videodev_open().  That function
itself seems OK, but one never knows about all the open() functions
provided by underlying video drivers.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Add explicit lock_kernel() calls to usbdev_open()
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Add explicit lock_kernel() calls to mon_bin_open()
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Add explicit lock_kernel() calls to printer_open()
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Put explicit lock_kernel() calls in adb_open().  The fact that
adb_release() already has them suggests this is necessary.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Put explicit lock_kernel() calls into maint_open().
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Put explicit lock_kernel() calls into capi_open()
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Add lock_kernel() calls to ch_open(), though the existing locking looks
adequate.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Add lock_kernel() calls to adpt_open()
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Add explicit lock_kernel() calls to vfc_open().
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Put explicit lock_kernel() calls into bpp_open().  It has locking, but I'm
not convinced it won't race with ioctl().
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Add explicit lock_kernel calls to phantom_open().
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Be extra-cautious and protect the remaining open() functions.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Put explicit lock_kernel calls into dsp56k_open().

[Stupid missing label error fixed]
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Put explicit lock_kernel() calls into raw_open(), even though the existing
locking looks adequate.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Put explicit lock_kernel calls into tlclk_open()
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Add explicit lock_kernel() calls to hwicap_open() even though the existing
locking looks adequate.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Add explicit BKL to vcs_open().
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Add the BKL to spidev_open(), even though the existing locking looks
adequate.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

This documents the fact that somebody looked at the relevant open()
functions and concluded that, due to their trivial nature, no locking was
needed.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Parts of the serial code actually BUG() if we don't do this.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

usb_open() is protected by a down_read(&minor_rwsem), but I'm not sure I
trust it to protect everything including subsidiary open() functions.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

->release() already has explicit lock_kernel() calls...
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

phone_open() looks OK, but I don't trust the subsidiary drivers (and ixj in
particular).
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

This driver would appear to have no internal locking at all.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

misc_open() looks fine, but who knows what all of the misc drivers are
doing in their open() functions?
Signed-off-by: Jonathan Corbet <corbet@lwn.net>