Application Hangs in Flash Player 30

Question

I have an application that works just fine in Flash player 29 in all browsers and does not work in Flash player 30 in any browsers. My app doesn't use any of the restricted methods that were in scope for the version 30 release. I've put trace statements in my code and can attach the debugger to it, however, when it freezes the debugger doesn't give any output or errors and the trace statements don't output text any more. It's very bizarre and frustrating. We have other Flash apps that work just fine with version 30 but this single app no longer works in version 30.

I've experienced instances where stepping through the code in the debugger will result in the app working on occasion, it's not clear whether that's due to a timing issue introduced by stepping through the code or if there's some other factor at play.

What's the best way to get to the bottom of this problem and determine a fix? The guidance we've giving our users is to downgrade to version 29, which isn't a path that many people are able to do due to corporate restrictions or other factors.

jeromiec83223024 · Accepted Answer

My guess is that this is related to the timer or event jitter mitigations that were deployed in Flash Player 30; however, those changes typically introduce something on the order of 100 microseconds of delay per call. If you're only calling them once every couple milliseconds, you shouldn't really feel it.

It would be interesting to know if one of these two mms.cfg directives make the problem go away:

EventJitterMicroseconds = 0

TimerJitterMicroseconds = 0

If they do, my suspicion would be that something is throwing events or polling a timer quite a bit faster than expected. That may be happening under the hood, but I haven't heard anyone complaining about setTimeout up until now. If you could share a snippet that gets to the heart of it (I don't want to guess about the specifics of what you might have implemented if I can avoid it), I'd definitely be interested in looking into it further.

jeromiec83223024 · Answer

Thanks for the update.

The intent is definitely not to get end-users to set these flags. They're a nice troubleshooting measure for determining what to look at, and possibly as a workaround for enterprise organizations with large deployment that might need to mitigate the impact to an internal tool or something.

Unfortunately, these mitigations are necessary and aren't going away, and I'm not optimistic that we'd be able to optimize for this use-case while still maintaining the integrity of the original mitigation.

If you're a content provider, the best solution is going to be to update your code to avoid calling timers in tight loops. In this instance, setting the timer recursively probably unrolls into a long sequence of timer calls that proves similarly problematic.

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