kernel oops!  when unregister_kprobe() is called on a non-registered
kprobe.  This patch fixes the above problem by checking if the probe exists
before unregistering.
Signed-off-by: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>