[GROOVY-4736] Deadlock when GroovyClassLoader is used in multi-threaded environment

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 1.7.9
• Component/s: groovy-runtime
• Labels: closeifnofeedback
• Environment: Multiple OS: development server: Ubuntu 32-bit, desktop machine: Windows 7 64-bit, Java 1.6 Update 21
• Assignee: Jochen Theodorou
• Reporter: Szymon Kuklewicz
• Created: 19/Mar/11 07:51
• Updated: 04/Mar/14 16:31
• Resolved: 29/Jan/14 09:10

Description

When multiple threads uses GroovyClassLoader to get Groovy classes or just work with them (instantiation, etc.) and an other(s) threads change the sources (followed by clearCache call), then deadlock can happen related to synchronizations on InnerLoader and HashMap (GroovyClassLoader.sourceCache)

I attached simple test scenation when 3 threads load Groovy classes and instantiate them and 3 other threads replace sources and call GroocyClassLoader.clearCache(). There is a synchronization on writeToFile to be ensure that the same file is not being written at the same time but this synchronization does not take part in a deadlock.

Please just run the test and wait a moment. Deadlock happens usually in 1 second at this test scenario. I hope this test will be also useful in Your future development as a standard test case.