diff options
Diffstat (limited to 'src/share/classes/com/sun/tools/jdi/ThreadReferenceImpl.java')
| -rw-r--r-- | src/share/classes/com/sun/tools/jdi/ThreadReferenceImpl.java | 114 |
1 files changed, 72 insertions, 42 deletions
diff --git a/src/share/classes/com/sun/tools/jdi/ThreadReferenceImpl.java b/src/share/classes/com/sun/tools/jdi/ThreadReferenceImpl.java index 7af01561e..0f18120f1 100644 --- a/src/share/classes/com/sun/tools/jdi/ThreadReferenceImpl.java +++ b/src/share/classes/com/sun/tools/jdi/ThreadReferenceImpl.java @@ -61,7 +61,8 @@ public class ThreadReferenceImpl extends ObjectReferenceImpl private ThreadGroupReference threadGroup; // This is cached only while this one thread is suspended. Each time - // the thread is resumed, we clear this and start with a fresh one. + // the thread is resumed, we abandon the current cache object and + // create a new intialized one. private static class LocalCache { JDWP.ThreadReference.Status status = null; List<StackFrame> frames = null; @@ -74,6 +75,28 @@ public class ThreadReferenceImpl extends ObjectReferenceImpl boolean triedCurrentContended = false; } + /* + * The localCache instance var is set by resetLocalCache to an initialized + * object as shown above. This occurs when the ThreadReference + * object is created, and when the mirrored thread is resumed. + * The fields are then filled in by the relevant methods as they + * are called. A problem can occur if resetLocalCache is called + * (ie, a resume() is executed) at certain points in the execution + * of some of these methods - see 6751643. To avoid this, each + * method that wants to use this cache must make a local copy of + * this variable and use that. This means that each invocation of + * these methods will use a copy of the cache object that was in + * effect at the point that the copy was made; if a racy resume + * occurs, it won't affect the method's local copy. This means that + * the values returned by these calls may not match the state of + * the debuggee at the time the caller gets the values. EG, + * frameCount() is called and comes up with 5 frames. But before + * it returns this, a resume of the debuggee thread is executed in a + * different debugger thread. The thread is resumed and running at + * the time that the value 5 is returned. Or even worse, the thread + * could be suspended again and have a different number of frames, eg, 24, + * but this call will still return 5. + */ private LocalCache localCache; private void resetLocalCache() { @@ -129,8 +152,9 @@ public class ThreadReferenceImpl extends ObjectReferenceImpl } /** - * Note that we only cache the name string while suspended because - * it can change via Thread.setName arbitrarily + * Note that we only cache the name string while the entire VM is suspended + * because the name can change via Thread.setName arbitrarily while this + * thread is running. */ public String name() { String name = null; @@ -240,19 +264,20 @@ public class ThreadReferenceImpl extends ObjectReferenceImpl } private JDWP.ThreadReference.Status jdwpStatus() { - JDWP.ThreadReference.Status myStatus = localCache.status; + LocalCache snapshot = localCache; + JDWP.ThreadReference.Status myStatus = snapshot.status; try { if (myStatus == null) { myStatus = JDWP.ThreadReference.Status.process(vm, this); if ((myStatus.suspendStatus & SUSPEND_STATUS_SUSPENDED) != 0) { // thread is suspended, we can cache the status. - localCache.status = myStatus; + snapshot.status = myStatus; } } } catch (JDWPException exc) { throw exc.toJDIException(); } - return myStatus; + return myStatus; } public int status() { @@ -304,9 +329,10 @@ public class ThreadReferenceImpl extends ObjectReferenceImpl } public int frameCount() throws IncompatibleThreadStateException { + LocalCache snapshot = localCache; try { - if (localCache.frameCount == -1) { - localCache.frameCount = JDWP.ThreadReference.FrameCount + if (snapshot.frameCount == -1) { + snapshot.frameCount = JDWP.ThreadReference.FrameCount .process(vm, this).frameCount; } } catch (JDWPException exc) { @@ -318,7 +344,7 @@ public class ThreadReferenceImpl extends ObjectReferenceImpl throw exc.toJDIException(); } } - return localCache.frameCount; + return snapshot.frameCount; } public List<StackFrame> frames() throws IncompatibleThreadStateException { @@ -335,22 +361,22 @@ public class ThreadReferenceImpl extends ObjectReferenceImpl * local is known to be non-null. Should only be called from * a sync method. */ - private boolean isSubrange(LocalCache localCache, + private boolean isSubrange(LocalCache snapshot, int start, int length) { - if (start < localCache.framesStart) { + if (start < snapshot.framesStart) { return false; } if (length == -1) { - return (localCache.framesLength == -1); + return (snapshot.framesLength == -1); } - if (localCache.framesLength == -1) { - if ((start + length) > (localCache.framesStart + - localCache.frames.size())) { + if (snapshot.framesLength == -1) { + if ((start + length) > (snapshot.framesStart + + snapshot.frames.size())) { throw new IndexOutOfBoundsException(); } return true; } - return ((start + length) <= (localCache.framesStart + localCache.framesLength)); + return ((start + length) <= (snapshot.framesStart + snapshot.framesLength)); } public List<StackFrame> frames(int start, int length) @@ -371,14 +397,14 @@ public class ThreadReferenceImpl extends ObjectReferenceImpl // Lock must be held while creating stack frames so if that two threads // do this at the same time, one won't clobber the subset created by the other. - + LocalCache snapshot = localCache; try { - if (localCache.frames == null || !isSubrange(localCache, start, length)) { + if (snapshot.frames == null || !isSubrange(snapshot, start, length)) { JDWP.ThreadReference.Frames.Frame[] jdwpFrames = JDWP.ThreadReference.Frames. process(vm, this, start, length).frames; int count = jdwpFrames.length; - localCache.frames = new ArrayList<StackFrame>(count); + snapshot.frames = new ArrayList<StackFrame>(count); for (int i = 0; i<count; i++) { if (jdwpFrames[i].location == null) { @@ -388,20 +414,20 @@ public class ThreadReferenceImpl extends ObjectReferenceImpl jdwpFrames[i].frameID, jdwpFrames[i].location); // Add to the frame list - localCache.frames.add(frame); + snapshot.frames.add(frame); } - localCache.framesStart = start; - localCache.framesLength = length; - return Collections.unmodifiableList(localCache.frames); + snapshot.framesStart = start; + snapshot.framesLength = length; + return Collections.unmodifiableList(snapshot.frames); } else { - int fromIndex = start - localCache.framesStart; + int fromIndex = start - snapshot.framesStart; int toIndex; if (length == -1) { - toIndex = localCache.frames.size() - fromIndex; + toIndex = snapshot.frames.size() - fromIndex; } else { toIndex = fromIndex + length; } - return Collections.unmodifiableList(localCache.frames.subList(fromIndex, toIndex)); + return Collections.unmodifiableList(snapshot.frames.subList(fromIndex, toIndex)); } } catch (JDWPException exc) { switch (exc.errorCode()) { @@ -415,15 +441,16 @@ public class ThreadReferenceImpl extends ObjectReferenceImpl } public List<ObjectReference> ownedMonitors() throws IncompatibleThreadStateException { + LocalCache snapshot = localCache; try { - if (localCache.ownedMonitors == null) { - localCache.ownedMonitors = Arrays.asList( + if (snapshot.ownedMonitors == null) { + snapshot.ownedMonitors = Arrays.asList( (ObjectReference[])JDWP.ThreadReference.OwnedMonitors. process(vm, this).owned); if ((vm.traceFlags & vm.TRACE_OBJREFS) != 0) { vm.printTrace(description() + " temporarily caching owned monitors"+ - " (count = " + localCache.ownedMonitors.size() + ")"); + " (count = " + snapshot.ownedMonitors.size() + ")"); } } } catch (JDWPException exc) { @@ -435,54 +462,57 @@ public class ThreadReferenceImpl extends ObjectReferenceImpl throw exc.toJDIException(); } } - return localCache.ownedMonitors; + return snapshot.ownedMonitors; } public ObjectReference currentContendedMonitor() throws IncompatibleThreadStateException { + LocalCache snapshot = localCache; try { - if (localCache.contendedMonitor == null && - !localCache.triedCurrentContended) { - localCache.contendedMonitor = JDWP.ThreadReference.CurrentContendedMonitor. + if (snapshot.contendedMonitor == null && + !snapshot.triedCurrentContended) { + snapshot.contendedMonitor = JDWP.ThreadReference.CurrentContendedMonitor. process(vm, this).monitor; - localCache.triedCurrentContended = true; - if ((localCache.contendedMonitor != null) && + snapshot.triedCurrentContended = true; + if ((snapshot.contendedMonitor != null) && ((vm.traceFlags & vm.TRACE_OBJREFS) != 0)) { vm.printTrace(description() + " temporarily caching contended monitor"+ - " (id = " + localCache.contendedMonitor.uniqueID() + ")"); + " (id = " + snapshot.contendedMonitor.uniqueID() + ")"); } } } catch (JDWPException exc) { switch (exc.errorCode()) { + case JDWP.Error.THREAD_NOT_SUSPENDED: case JDWP.Error.INVALID_THREAD: /* zombie */ throw new IncompatibleThreadStateException(); default: throw exc.toJDIException(); } } - return localCache.contendedMonitor; + return snapshot.contendedMonitor; } public List<MonitorInfo> ownedMonitorsAndFrames() throws IncompatibleThreadStateException { + LocalCache snapshot = localCache; try { - if (localCache.ownedMonitorsInfo == null) { + if (snapshot.ownedMonitorsInfo == null) { JDWP.ThreadReference.OwnedMonitorsStackDepthInfo.monitor[] minfo; minfo = JDWP.ThreadReference.OwnedMonitorsStackDepthInfo.process(vm, this).owned; - localCache.ownedMonitorsInfo = new ArrayList<MonitorInfo>(minfo.length); + snapshot.ownedMonitorsInfo = new ArrayList<MonitorInfo>(minfo.length); for (int i=0; i < minfo.length; i++) { JDWP.ThreadReference.OwnedMonitorsStackDepthInfo.monitor mi = minfo[i]; MonitorInfo mon = new MonitorInfoImpl(vm, minfo[i].monitor, this, minfo[i].stack_depth); - localCache.ownedMonitorsInfo.add(mon); + snapshot.ownedMonitorsInfo.add(mon); } if ((vm.traceFlags & vm.TRACE_OBJREFS) != 0) { vm.printTrace(description() + " temporarily caching owned monitors"+ - " (count = " + localCache.ownedMonitorsInfo.size() + ")"); + " (count = " + snapshot.ownedMonitorsInfo.size() + ")"); } } @@ -495,7 +525,7 @@ public class ThreadReferenceImpl extends ObjectReferenceImpl throw exc.toJDIException(); } } - return localCache.ownedMonitorsInfo; + return snapshot.ownedMonitorsInfo; } public void popFrames(StackFrame frame) throws IncompatibleThreadStateException { |