bitbake: runqueue: Fix dependency loop analysis 'hangs'

Currently the mechanism for breaking out of the dependnecy loop analysis
code is broken and doesn't work leading to bitbake appearing to hang.

Add in a custom exception for this purpose and fix the code to exit
as intended, fixing the hang and making the dependency loop code
usable again.

(Bitbake rev: e39dbd72ef44eebae32f9fe3b75a1bf789605558)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/runqueue.py

@@ -405,6 +405,9 @@ class RunQueueData:
         explored_deps = {}
         msgs = []
 
+        class TooManyLoops(Exception):
+            pass
+
         def chain_reorder(chain):
             """
             Reorder a dependency chain so the lowest task id is first
@@ -457,7 +460,7 @@ class RunQueueData:
                         msgs.append("\n")
                     if len(valid_chains) > 10:
                         msgs.append("Aborted dependency loops search after 10 matches.\n")
-                        return msgs
+                        raise TooManyLoops
                     continue
                 scan = False
                 if revdep not in explored_deps:
@@ -476,8 +479,11 @@ class RunQueueData:
 
             explored_deps[tid] = total_deps
 
-        for task in tasks:
-            find_chains(task, [])
+        try:
+            for task in tasks:
+                find_chains(task, [])
+        except TooManyLoops:
+            pass
 
         return msgs