tree 704d05a8f75181f548d67e811d0e3993b2014334
parent bda965bc263e873323e68a09628fddced620f810
author Chris Morin <cmtm@google.com> 1523669293 -0700
committer ChromeOS Commit Bot <chromeos-commit-bot@chromium.org> 1524080418 +0000

login: change implementation of asynchronous Upstart events

The way Upstart was being triggered could lead to two event emissions
called in a certain order being sent to Upstart via D-Bus in the
reversed order. This could occur if the first one is ASYNC and the
second is SYNC.  SYNC messages were being sent directly to D-Bus and
blocking the main thread until the response was received, whereas ASYNC
messages were posted to to the message loop queue where they would be
later sent to D-Bus.  This caused the order in which messages were
delivered to D-Bus to not match developer's expectations.

With this change, the D-Bus messages are always sent synchronously and
block until they are acknowledged by Upstart, but the ASYNC events now
set the Upstart's wait flag to false to return as soon as the event is
queued. This causes the events to be delivered in the right order.

BUG=b:77528877
TEST=Reproduce conditions causing bug and ensure error isn't seen

Change-Id: I32e9d62a8c7ee86ff781890189d0a14c3be291ee
Reviewed-on: https://chromium-review.googlesource.com/1017700
Reviewed-by: Christopher Morin <cmtm@google.com>
Commit-Queue: Christopher Morin <cmtm@google.com>
Tested-by: Christopher Morin <cmtm@google.com>
Trybot-Ready: Christopher Morin <cmtm@google.com>