Documentation: Clarify when module debugging actually works.

Signed-off-by: NRobert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: NAdrian Bunk <bunk@kernel.org>

Documentation/debugging-modules.txt

@@ -16,3 +16,7 @@ echo 'echo "$@" >> /tmp/modprobe.log' >> /tmp/modprobe
 echo 'exec /sbin/modprobe "$@"' >> /tmp/modprobe
 chmod a+x /tmp/modprobe
 echo /tmp/modprobe > /proc/sys/kernel/modprobe
+
+Note that the above applies only when the *kernel* is requesting
+that the module be loaded -- it won't have any effect if that module
+is being loaded explicitly using "modprobe" from userspace.