Hi Andrew,
The patch itself looks reasonable.
However, in order to proceed with it, a bug report with a standalone
test case demonstrating the issue is needed.
Thanks,
Serguei
On 4/9/18 09:07, Andrew Leonard wrote:
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
