lib/oe/utils: Add utils function for multiprocess execution

Our usage of multitprocessing is problematic. In particular, there is a bug
in python 2.7 multiprocessing where signals are not handled until command
completion instead of immediately.

This factors the multiprocess code into a function which is enhanced with
a workaround to ensure immediate signal handling and also better SIGINT
handling which should happen in the parent, not the children to ensure
clean exits. The workaround for the signals is being added to the core
bb.utils function so it can benefit all users.

package_manager is then converted to use the new code.

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

1 files changed, 29 insertions, 0 deletions

diff --git a/meta/lib/oe/utils.py b/meta/lib/oe/utils.py
index 0a1d1080c9..92e21a4e0e 100644
--- a/meta/lib/oe/utils.py
+++ b/meta/lib/oe/utils.py
@@ -151,3 +151,32 @@ def execute_pre_post_process(d, cmds):
         if cmd != '':
             bb.note("Executing %s ..." % cmd)
             bb.build.exec_func(cmd, d)
+
+def multiprocess_exec(commands, function):
+    import signal
+    import multiprocessing
+
+    if not commands:
+        return []
+
+    def init_worker():
+        signal.signal(signal.SIGINT, signal.SIG_IGN)
+
+    nproc = min(multiprocessing.cpu_count(), len(commands))
+    pool = bb.utils.multiprocessingpool(nproc, init_worker)
+    imap = pool.imap(function, commands)
+
+    try:
+        results = list(imap)
+        pool.close()
+        pool.join()
+        results = []
+        for result in results:
+            if result is not None:
+                results.append(result)
+        return results
+
+    except KeyboardInterrupt:
+        pool.terminate()
+        pool.join()
+        raise