The UP.rst file calls for locks acquired within RCU callback functions
to use _irq variants (spin_lock_irqsave() or similar), which does work,
but can be overkill.  This commit therefore instead calls for _bh variants
(spin_lock_bh() or similar), while noting that _irq does work.
Signed-off-by: NPaul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: NJiunn Chang <c0d1n61at3@gmail.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>