Invisible race conditionsThe sometimes failing script
time to read 1 min | 167 words

You probably know that Chrome is a memory hog, I came up with the following extremely brute force manner to deal with it:

This works quite nicely in 99% of the cases, but sometimes, this fails. Can you see why?

I’ll give you a hint, the EmptyWorkingSet() returns a failure and an invalid handle error . Why is that?

Well, the problem is a bit tricky. We first execute the Get-Process cmdlet, and extract the handles from the results. That is great, but we don’t keep track of the Process instances that we get from Get-Process, which means that they are garbage.

That means that the GC might clean them, but they require finalization, so at some point, the finalizer will claim them, closing their handles, which means that the EmptyWorkingSet will fail sporadically in a very non obvious way. The “fix”, by the way, is to iterate of the processes directly, not on their handles, because that keep the process instance live for the duration (and thus its handle).

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More posts in "Invisible race conditions" series:

  1. (02 Jan 2018) The cache has poisoned us
  2. (27 Dec 2017) The sometimes failing script
  3. (26 Dec 2017) The async query