store_stackinfo() does an unlocked module list walk during normal runtime
which opens up a race with the module load/unload code.  This can be
triggered by simply unloading and loading a module in a loop with
CONFIG_DEBUG_PAGEALLOC resulting in store_stackinfo() tripping over bad
list pointers.

kernel_text_address doesn't take any locks, because during an OOPS we don't
want to deadlock.  Rename that to __kernel_text_address, and make
kernel_text_address take the lock.
Signed-off-by: Zwane Mwaikambo <zwane@fsmlabs.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (modified)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>