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Here's a stack trace: https://gist.github.com/duncanmak/e339125e83727113feab
That looks perfectly normal to me. This is not xbuild, it's Xamarin Studio's MSBuild/xbuild hosting helper process, and it's waiting for commands from its parent.
Need a backtrace of the parent process.
The parent mdtool is a zombie.
The problem here, as I see it, is that either mdtool is not waiting enough for its children to exit or those child processes are not detecting the defunct parent.
The situation is the following, we have 3 processes in a hierarchy:
(1)shell -> (2) mdtool -> (3)XS xbuild *thing*
Process (2) exits and turn into a zombie
Process (3) is hang as per the above dump
The zombification happens because (2) has a child (3) that is still running.
Given the above background, I see a few options here:
It's a bug in (2)
It a bug in (3)
It's a runtime bug that causes (2) to misbehave
It's a runtime bug that causes (3) to misbehave
I'm pretty sure it's a runtime regression. It used to be that the parent could exit (e.g. crash) and the child would be left running, so child specifically polls the parent PID so it can exit when the parent exits. The parent does not wait for the child.
Perfect, can you point me to the code that performs this polling so I can try to extract a test-case?
Duncan, what mono version are you trying this with?
duncan@duncans-imac:CocosSharp ((23c3862...))$ mono --version
Mono JIT compiler version 3.2.3 ((no/8d3b4b7 Mon Sep 16 23:46:28 EDT 2013)
Copyright (C) 2002-2012 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
Michael provided a test case.
That piece of code is a thousand miles away from been a test case. Anyhow, will take a look.
This is a build script bug.
Rodrigo, can you tell us how to fix it, or what the bug was?