[OE-core] [PATCH 2/3] lib/oe/utils: Handle exceptions in multiprocess_exec

[Richard Purdie]

Currently exceptions that happen in pool commands are ignored. Any errors
would be printed on the console but everything else is silent.

Switch to use pool.map_async which allows for an error_callback which
we can use to detect exceptions and make sure these errors are handled.

Signed-off-by: Richard Purdie <richard.purdie at linuxfoundation.org>
---
 meta/lib/oe/utils.py | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/meta/lib/oe/utils.py b/meta/lib/oe/utils.py
index 822d0cd..643ab78 100644
--- a/meta/lib/oe/utils.py
+++ b/meta/lib/oe/utils.py
@@ -224,25 +224,30 @@ def multiprocess_exec(commands, function):
     def init_worker():
         signal.signal(signal.SIGINT, signal.SIG_IGN)
 
+    fails = []
+
+    def failures(res):
+        fails.append(res)
+
     nproc = min(multiprocessing.cpu_count(), len(commands))
     pool = bb.utils.multiprocessingpool(nproc, init_worker)
-    imap = pool.imap(function, commands)
 
     try:
-        res = list(imap)
+        mapresult = pool.map_async(function, commands, error_callback=failures)
+
         pool.close()
         pool.join()
-        results = []
-        for result in res:
-            if result is not None:
-                results.append(result)
-        return results
-
+        results = mapresult.get()
     except KeyboardInterrupt:
         pool.terminate()
         pool.join()
         raise
 
+    if fails:
+        raise fails[0]
+
+    return results
+
 def squashspaces(string):
     import re
     return re.sub("\s+", " ", string).strip()
-- 
2.7.4