Hi,
We discovered in our testing with OpenJ9 that a race condition can occur
in the jdwp under certain circumstances, and we were able to force the
same issue with Hotspot. Normally, the event helper thread suspends all
threads, then the debug loop in the listener thread receives a command to
resume. The debugger may deadlock if the debug loop in the listener thread
starts processing commands (e.g. resume threads) before the event helper
completes the initialization (and suspends threads).
This patch adds synchronization to ensure the event helper completes the
initialization sequence before debugger commands are processed.
Please can I find a sponsor for this contribution? Patch below..
Many thanks
Andrew
diff --git a/src/jdk.jdwp.agent/share/native/libjdwp/debugInit.c
b/src/jdk.jdwp.agent/share/native/libjdwp/debugInit.c
--- a/src/jdk.jdwp.agent/share/native/libjdwp/debugInit.c
+++ b/src/jdk.jdwp.agent/share/native/libjdwp/debugInit.c
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 1998, 2017, Oracle and/or its affiliates. All rights
reserved.
+ * Copyright (c) 1998, 2018, Oracle and/or its affiliates. All rights
reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -58,6 +58,7 @@
static jboolean vmInitialized;
static jrawMonitorID initMonitor;
static jboolean initComplete;
+static jboolean VMInitComplete;
static jbyte currentSessionID;
/*
@@ -617,6 +618,35 @@
debugMonitorExit(initMonitor);
}
+/*
+ * Signal VM initialization is complete.
+ */
+void
+signalVMInitComplete(void)
+{
+ /*
+ * VM Initialization is complete
+ */
+ LOG_MISC(("signal VM initialization complete"));
+ debugMonitorEnter(initMonitor);
+ VMInitComplete = JNI_TRUE;
+ debugMonitorNotifyAll(initMonitor);
+ debugMonitorExit(initMonitor);
+}
+
+/*
+ * Wait for VM initialization to complete.
+ */
+void
+debugInit_waitVMInitComplete(void)
+{
+ debugMonitorEnter(initMonitor);
+ while (!VMInitComplete) {
+ debugMonitorWait(initMonitor);
+ }
+ debugMonitorExit(initMonitor);
+}
+
/* All process exit() calls come from here */
void
forceExit(int exit_code)
@@ -672,6 +702,7 @@
LOG_MISC(("Begin initialize()"));
currentSessionID = 0;
initComplete = JNI_FALSE;
+ VMInitComplete = JNI_FALSE;
if ( gdata->vmDead ) {
EXIT_ERROR(AGENT_ERROR_INTERNAL,"VM dead at initialize() time");
diff --git a/src/jdk.jdwp.agent/share/native/libjdwp/debugInit.h
b/src/jdk.jdwp.agent/share/native/libjdwp/debugInit.h
--- a/src/jdk.jdwp.agent/share/native/libjdwp/debugInit.h
+++ b/src/jdk.jdwp.agent/share/native/libjdwp/debugInit.h
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 1998, 2015, Oracle and/or its affiliates. All rights
reserved.
+ * Copyright (c) 1998, 2018, Oracle and/or its affiliates. All rights
reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -39,4 +39,7 @@
void debugInit_exit(jvmtiError, const char *);
void forceExit(int);
+void debugInit_waitVMInitComplete(void);
+void signalVMInitComplete(void);
+
#endif
diff --git a/src/jdk.jdwp.agent/share/native/libjdwp/debugLoop.c
b/src/jdk.jdwp.agent/share/native/libjdwp/debugLoop.c
--- a/src/jdk.jdwp.agent/share/native/libjdwp/debugLoop.c
+++ b/src/jdk.jdwp.agent/share/native/libjdwp/debugLoop.c
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 1998, 2017, Oracle and/or its affiliates. All rights
reserved.
+ * Copyright (c) 1998, 2018, Oracle and/or its affiliates. All rights
reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -98,6 +98,7 @@
standardHandlers_onConnect();
threadControl_onConnect();
+ debugInit_waitVMInitComplete();
/* Okay, start reading cmds! */
while (shouldListen) {
if (!dequeue(&p)) {
diff --git a/src/jdk.jdwp.agent/share/native/libjdwp/eventHelper.c
b/src/jdk.jdwp.agent/share/native/libjdwp/eventHelper.c
--- a/src/jdk.jdwp.agent/share/native/libjdwp/eventHelper.c
+++ b/src/jdk.jdwp.agent/share/native/libjdwp/eventHelper.c
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 1998, 2017, Oracle and/or its affiliates. All rights
reserved.
+ * Copyright (c) 1998, 2018, Oracle and/or its affiliates. All rights
reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -580,6 +580,7 @@
(void)threadControl_suspendThread(command->thread, JNI_FALSE);
}
+ signalVMInitComplete();
outStream_initCommand(&out, uniqueID(), 0x0,
JDWP_COMMAND_SET(Event),
JDWP_COMMAND(Event, Composite));
Andrew Leonard
Java Runtimes Development
IBM Hursley
IBM United Kingdom Ltd
Phone internal: 245913, external: 01962 815913
internet email: andrew_m_leon...@uk.ibm.com
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
