TPL and the case of the !@#(*@! hung process
So, here I am writing some really fun code, when I found out that I am running into dead locks in the code. I activate emergency protocols and went into deep debugging mode.
After being really through in figuring out several possible causes, I was still left with what is effectively a WTF @!(*!@ DAMN !(@*#!@* YOU !@*!@( outburst and a sudden longing for something to repeatedly hit.
Eventually, however, I figure out what was going on.
I have the following method: Aggregator.AggregateAsync(), inside which we have a call to the PulseAll method. That method will then go and execute the following code:
After that, I return from the method. In another piece of the code (Aggregator.Dispose) I am waiting for the task that is running the AggregateAsync method to complete.
Nothing worked! It took me a while before I figured out that I wanted to check the stack, where I found this:
Basically, I had a dead lock because when I called SetResult on the completion source (which freed the Dispose code to run), I actually switched over to that task and allowed it to run. Still in the same thread, but in a different task, I run through the rest of the code and eventually got to the Aggregator.Dispose(). Now, I could only get to it if it the PulseAll() method was called. But, because we are on the same thread, that task hasn’t been completed yet!
In the end, I “solved” that by introducing a DisposeAsync() method, which allowed us to yield the thread, and then the AggregateAsync task was completed, and then we could move on.
But I am really not very happy about this. Any ideas about proper way to handle async & IDisposable?