[Vm-dev] Frequent SegFaults in PharoVM with Pharo 3.0

Max Leske maxleske at gmail.com
Wed Nov 6 21:04:18 UTC 2013


We’ve been encountering frequent SegFaults when running the Fuel tests on the Pharo CI (https://ci.inria.fr/pharo-contribution/job/Fuel/). Since today I’ve also been able to reproduce the SegFaults on my MacBook Pro (OS X 10.9) too. We have not been able to determine the cause of the SegFault but we can produce SegFaults often, although not reliable (more reliable on the CI).

The CI uses the stable VM: http://files.pharo.org/vm/pharo/linux/stable.zip
I use a newer version from October on my machine: http://files.pharo.org/vm/pharo/mac/273.zip

I’ve attached all the dumps of the crashes I was able to produce on my machine, together with Apple’s crash logs.

I’ve been able to deduce the following:
- garbage collection seems to be a trigger for the SegFault. When one of the methods FLMethodContextSerialization>>testFuelShouldIgnoreFuel and FLMethodContextSerialization>>testMethodContextWithNilPc contain the line “3 timesRepeat: [Smalltalk garbageCollect]” the SegFault appears nearly always (on CI). When I remove the line the builds run through.
- Not all methods with the garbage collect line trigger a SegFault (I could only identify those two)
- the garbage collect line itself suffices as a trigger in the mentioned methods.
- The number of tests (amount of used memory?) seems to influence the appearence of the SegFault (e.g. loading "DevelopmentGroup" seems to trigger it more often than loading “Benchmarks”)
- the SegFault always appears after the tests with the garbage collect line have been run, never before
- the VM can’t write the crash.dmp every time

Since the SegFaults are so random I cannot give you an image to reproduce the problem. I’ve had the best results using a fresh 3.0 image (http://files.pharo.org/image/30/30549.zip) and then evaluating the following in a workspace:

Gofer it
	smalltalkhubUser: 'Pharo' project:  'Fuel';
	package: 'ConfigurationOfFuel';
((Smalltalk at: #ConfigurationOfFuel) project version: #bleedingEdge) load: 'DevelopmentGroup'.

	runClasses: (TestCase allSubclasses select: [ :class | class name beginsWith: 'FL'])
	named: ‘foo'

If it doesn’t work, try using the TestRunner manually. Select the default Fuel tests (alphabetically at F) and the additional Fuel tests (at the bottom of the list) and run them.

If anybody has any clue about what could be going on I’d really appreciate any input. I’ll happily provide more information if I can.

Thanks for reading :)

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