[PATCH] unwinder: Add debugging output to the Dwarf2 unwinder

Add debugging printks to the unwinder to allow easier debugging
when something goes wrong with it.

This can be controlled with the new unwinder_debug=N option
Most output is given by N=1

AK: Added documentation of unwinder_debug=
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>

Documentation/kernel-parameters.txt

@@ -1735,6 +1735,9 @@ and is between 256 and 4096 characters. It is defined in the file
 	norandmaps	Don't use address space randomization
 			Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
 
+ 	unwind_debug=N 	N > 0 will enable dwarf2 unwinder debugging
+			This is useful to get more information why
+			you got a "dwarf2 unwinder stuck"
 
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