Hi Andrew,
I've filed the bug:
https://bugs.openjdk.java.net/browse/JDK-8201409
Also, this is a webrev with your patch:
http://cr.openjdk.java.net/~sspitsyn/webrevs/2018/8201409-jdwp-initsync.ibm.1/
I agree that creating a standalone test is tricky here.
I've added usleep(10000) into the eventHelper_reportVMInit()
and ran the JTreg com/sun/jdi tests with my JDK build.
However, none of the tests failed with the failure mode you
described.
So that I'm puzzled a little bit.
I suspect that some specific debugLoop commands were used in your
scenario.
It is still possible that I've missed something here.
Will try to double check everything.
Thanks,
Serguei
On 4/11/18 01:29, Andrew Leonard wrote:
Thanks Serguei,
I terms of a standalone
testcase it is quite tricky, as due to the nature of the issue
which took
a lot of investigation to solve it's very timing dependent and
will only
occur randomly. It can be forced as I indicated below by adding
a "sleep"
in the VMInit report code but that's not a testcase, however the
issue
was originally found in our JCK testing for IBMJava8, testcase test.jck8b.runtime.vm.jdwp,
but again only happened intermittently. Sort of like
"performance"
type issues we're not always going to be able to create a
testcase that
will always "fail" if the fix is not present.
Your thoughts?
Cheers
Andrew
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
From:
"serguei.spit...@oracle.com"
<serguei.spit...@oracle.com>
To:
Andrew
Leonard <andrew_m_leon...@uk.ibm.com>
Cc:
serviceability-dev@openjdk.java.net
Date:
11/04/2018
01:02
Subject:
Re:
RFR: Fix race condition in jdwp
Hi Andrew,
Okay, I'll file a bug on this topic.
But do you have a standalone test demonstrating this issue?
Thanks,
Serguei
On 4/10/18 06:23, Andrew Leonard wrote:
Hi Serguei,
I don't have access to the bug database to raise one, are you
able to please?
Summary: JDWP debugger initialization hangs intermittently
Description: If during the JDWP setup initialization the VM
initialization
takes slightly longer than the main debug initialization thread
a "hang"
situation can occur. This has been seen in testcase
test.jck8b.runtime.vm.jdwp
and can also be recreated easily by adding a 10 second sleep to
the beginning
of the src/jdk.jdwp.agent/share/native/libjdwp/eventHelper.c
method eventHelper_reportVMInit()
.
First seen: JDK8
Recreated: JDK11
Thanks
Andrew
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
From: "serguei.spit...@oracle.com"
<serguei.spit...@oracle.com>
To: Andrew Leonard <andrew_m_leon...@uk.ibm.com>,
serviceability-dev@openjdk.java.net
Date: 09/04/2018 23:03
Subject: Re: RFR: Fix race condition in jdwp
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
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
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
|
