Mercurial > hg > Members > kono > jpf-core
comparison src/main/gov/nasa/jpf/util/json/JSONObject.java @ 24:6774e2e08d37
the fix I would have liked to avoid - apparently hotspot internally does nested locking during class init, which can lead to deadlocks such as described in http://ternarysearch.blogspot.ru/2013/07/static-initialization-deadlock.html. Actually, it's not a regular deadlock since core dumps still list the threads as runnable, althouth it doesn't seem to be a livelock either. In any case, it can be simulated by nested locking and clinit execution, and it is such a serious defect that we want to be able to catch it. The general mechanism is to replace the disparate (but properly ordered) direct clinit calls of the generic ClassInfo.initializeClass() with a single sythetic method that includes all required locking (bottom up), clinit calls / class status change (top down), and unlocking (top down). We also need to add a synthetic insn to defer changing the class status of classes that don't have clinits(), or otherwise the correct lock/unlock order will not amount to anything if the hierarchy is entered through one of the clinit-absent classes. Now we get proper deadlocks if there are concurrent cyclic dependencies during class resolution. However, this can be such a state exploder that we certainly don't want this as the default behavior, especially since it probably is hotspot specific. Nested class init locking is therefore controlled by jvm.nested_init and respective jvm.nested_init.include/exclude options. Added a NestedInitTest to demonstrate use. Thanks to Lilia Abdulina for bringing this long forgotten issue up
In the wake of nested locks, there were a number of cases to fix that implicitly relied on absent clinits because clients were not properly checking for re-execution (most notably java.util.Exchanger). This mostly came in through MJIEnv.newObject/ElementInfo. We might turn ClinitRequired into a handled exception at some point, to catch such cases during compilation.
Added a UnknownJPFClass exception (in analogy to ClinitRequired), to make clients aware of failed class load attempts/reasons.
fixed Exchanger peer, which was not giving up the lock when timing out. This is an example of a lockfree wait op that can time out. Basically, ThreadInfo.isWaiting() needs to be complemented by a isWaitingOrTimedOut(), and ElementInfo.notifies0() has to be aware of it
fixed NPE when setting report.probe_interval in tests, which was missing that it had to create a stat object
author | Peter Mehlitz <Peter.C.Mehlitz@nasa.gov> |
---|---|
date | Tue, 21 Apr 2015 00:34:15 -0700 |
parents | db918c531e6d |
children |
comparison
equal
deleted
inserted
replaced
23:db918c531e6d | 24:6774e2e08d37 |
---|---|
106 for (FieldInfo fi : ci.getDeclaredInstanceFields()) { | 106 for (FieldInfo fi : ci.getDeclaredInstanceFields()) { |
107 ClassInfo ciField = fi.getTypeClassInfo(); | 107 ClassInfo ciField = fi.getTypeClassInfo(); |
108 if (requiresClinitExecution(ciField, ti)){ | 108 if (requiresClinitExecution(ciField, ti)){ |
109 return true; | 109 return true; |
110 } | 110 } |
111 if (ciField.isArray()){ | |
112 ClassInfo ciComp = ciField.getComponentClassInfo(); | |
113 if (requiresClinitExecution(ciComp, ti)) { | |
114 return true; | |
115 } | |
116 } | |
111 } | 117 } |
112 | 118 |
113 ci = ci.getSuperClass(); | 119 ci = ci.getSuperClass(); |
114 } | 120 } |
115 | 121 |