1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/dom/browser-element/mochitest/priority/CAUTION Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,15 @@
1.4 +A word to the wise:
1.5 +
1.6 +You must ensure that if your test finishes successfully, no processes have
1.7 +priority FOREGROUND_HIGH.
1.8 +
1.9 +If you don't do this, expect to see tests randomly fail with mysterious
1.10 +FOREGROUND --> FOREGROUND priority transitions.
1.11 +
1.12 +What's happening in this case is that your FOREGROUND_HIGH process lives until
1.13 +the beginning of the next test. This causes the process started by the next
1.14 +test to have low CPU priority. Then the FOREGROUND_HIGH process dies, because
1.15 +its iframe gets GC'ed, and we transition the new test's process from low CPU
1.16 +priority to regular CPU priority.
1.17 +
1.18 +Ouch.
