1 files changed, 16 insertions, 1 deletions

diff --git a/arch/ia64/kernel/unwind.c b/arch/ia64/kernel/unwind.c
index f47217b1bb37..fed6afa2e8a9 100644
--- a/arch/ia64/kernel/unwind.c
+++ b/arch/ia64/kernel/unwind.c
@@ -1531,7 +1531,7 @@ build_script (struct unw_frame_info *info)
         struct unw_labeled_state *ls, *next;
         unsigned long ip = info->ip;
         struct unw_state_record sr;
-        struct unw_table *table;
+        struct unw_table *table, *prev;
         struct unw_reg_info *r;
         struct unw_insn insn;
         u8 *dp, *desc_end;
@@ -1560,11 +1560,26 @@ build_script (struct unw_frame_info *info)
 
         STAT(parse_start = ia64_get_itc());
 
+        prev = NULL;
         for (table = unw.tables; table; table = table->next) {
                 if (ip >= table->start && ip < table->end) {
+                        /*
+                         * Leave the kernel unwind table at the very front,
+                         * lest moving it breaks some assumption elsewhere.
+                         * Otherwise, move the matching table to the second
+                         * position in the list so that traversals can benefit
+                         * from commonality in backtrace paths.
+                         */
+                        if (prev && prev != unw.tables) {
+                                /* unw is safe - we're already spinlocked */
+                                prev->next = table->next;
+                                table->next = unw.tables->next;
+                                unw.tables->next = table;
+                        }
                         e = lookup(table, ip - table->segment_base);
                         break;
                 }
+                prev = table;
         }
         if (!e) {
                 /* no info, return default unwinder (leaf proc, no mem stack, no saved regs)  */