[PATCH] x86_64: Document backtracer selection options

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/Documentation/x86_64/boot-options.txt b/Documentation/x86_64/boot-options.txt
index 6887d44d2661..6da24e7a56cb 100644
--- a/Documentation/x86_64/boot-options.txt
+++ b/Documentation/x86_64/boot-options.txt
@@ -238,6 +238,13 @@ Debugging
   pagefaulttrace Dump all page faults. Only useful for extreme debugging
                 and will create a lot of output.
 
+  call_trace=[old|both|newfallback|new]
+                old: use old inexact backtracer
+                new: use new exact dwarf2 unwinder
+                both: print entries from both
+                newfallback: use new unwinder but fall back to old if it gets
+                        stuck (default)
+
 Misc
 
   noreplacement  Don't replace instructions with more appropriate ones