Hi Alex,
Just several minutes ago in another email I sent an updated patch on review
(please see email attached). The patch has reimplemented tests and no longer
uses JdbTest , so the changes you mentioned are no longer there. I also created
issue https://bugs.openjdk.java.net/browse/JDK-8211736 to address the missing
prompt problem.
Thanks!
--Daniil
On 10/4/18, 2:53 PM, "Alex Menkov" <alexey.men...@oracle.com> wrote:
On 10/04/2018 10:28, Chris Plummer wrote:
> On 10/4/18 5:12 AM, Gary Adams wrote:
>> In TTY.java do you need to force a simple prompt for the
>> breakpoint event output? What prevents currentThread from
>> being set at the time you are printing the prompt?
>>
>>
>> 103 // Print the prompt if suspend policy is
>> SUSPEND_EVENT_THREAD. In case of
>> 104 // SUSPEND_ALL policy this is handled by vmInterrupted()
>> method.
>> 105 if (be.request().suspendPolicy() ==
>> EventRequest.SUSPEND_EVENT_THREAD) {
>> 106 MessageOutput.println();
>> 107 MessageOutput.printPrompt();
> Normally the thread is suspended after the above code is executed:
>
> public void run() {
> EventQueue queue = Env.vm().eventQueue();
> while (connected) {
> try {
> EventSet eventSet = queue.remove();
> boolean resumeStoppedApp = false;
> EventIterator it = eventSet.eventIterator();
> while (it.hasNext()) {
> resumeStoppedApp |= !handleEvent(it.nextEvent());
> <--- calls the modified code above
> }
>
> if (resumeStoppedApp) {
> eventSet.resume();
> } else if (eventSet.suspendPolicy() ==
> EventRequest.SUSPEND_ALL) {
> setCurrentThread(eventSet); <------
> notifier.vmInterrupted();
> }
>
> However, it only calls setCurrentThread() for SUSPEND_ALL policies. So
> what Daniil has done here is make it print a simple prompt if the policy
> is SUSPEND_EVENT_THREAD. It's unclear to me what the actual debugger
> behavior is in this case. Don't we still suspend and get a prompt from
> which we can type in the next command? In this case, wouldn't you want a
> full prompt? Related to that question, why is vmInterrupted() only
> called if we suspend all threads, and not when we just suspend the
> thread that the breakpoint came in on?
Did a quick test
- run debuggee (suspended), connect jdb:
===========
VM Started: No frames on the current call stack
main[1] stop thread at myclass:71
Deferring breakpoint myclass:71.
It will be set after the class is loaded.
main[1] run
> Set deferred breakpoint myclass:71
Breakpoint hit:
=====
I.e. we get only "Breakpoint hit: " without any info about the thread
(and this doesn't look good), current thread is not set ("next" reports
"Nothing suspended.")
But if we handle SUSPEND_EVENT_THREAD like SUSPEND_ALL, we need to think
how to handle possible race conditions when there are 2 threads, each of
them is stopped by "stop thread at/in".
Some notes about the fix (actually about the tests as the fix itself
should be implemented):
JdbStopThreadWithTraceOnTest.java
70 jdb.command("stop thread at " + DEBUGGEE_CLASS + ":" + bpLine);
It would be better to introduce
public static JdbCommand JdbCommand.stopThreadAt(String targetClass, int
lineNum)
Actually may be it would be better to drop Jdb.command(String) - it's
required only by CommandCommentDelimiter (need to update it to use "new
JdbCommand(...)").
If the fix will require "simple prompt" reply, I'd make it JdbCommand
property (like JdbCommand.allowExit)
--alex
>
> Chris
>>
>>
>> In Jdb.java you allow the waiting for the simple prompt.
>> I don't see waitForSimplePrompt used in any existing tests.
>> Since it is only looking for a single character it could
>> produce false positives if the '>' was produced in the
>> output stream. Is this wait paired to the added prompt for the
>> break point event?
>>
>> 236 return waitForSimplePrompt ? waitForSimplePrompt(1,
>> cmd.allowExit) : waitForPrompt(1, cmd.allowExit);
>>
>> It might be a good idea to include a test with multiple
>> threads each with a breakpoint that will trigger SUSPEND_EVENT_THREAD
>> behavior.
>>
>> On 10/4/18, 12:29 AM, Daniil Titov wrote:
>>> Please review the changes that fix the deadlock in the debugger when
>>> the debugger is running with the tracing option on.
>>>
>>> The problem here is that when the tracing is on the "JDI Target VM
>>> Interface" thread (the thread that reads all replies and then
>>> notifies the thread that sent the request that the reply has been
>>> received) is waiting for a lock which is already acquired by the
>>> thread that sent the request and is waiting for reply.
>>>
>>> The fix itself is in
>>> src/jdk.jdi/share/classes/com/sun/tools/jdi/VMState.java.
>>>
>>> The patch also reverts the changes done in 8129348 "Debugger hangs in
>>> trace mode with TRACE_SENDS" in
>>> src/jdk.jdi/share/classes/com/sun/tools/jdi/InvokableTypeImpl.java
>>> since they address only a specific case (VM is suspended and static
>>> method is invoked) while the proposed fix also solves issue 8129348
>>> as well as issue 8193801 "Debugger hangs in trace mode for non-static
>>> methods".
>>>
>>> The changes include new tests for issues 8193879, 8193801 and 8129348.
>>>
>>> The changes in
>>> src/jdk.jdi/share/classes/com/sun/tools/example/debug/tty/TTY.java
>>> solve the problem that the prompt is not printed in the debugger
>>> output when the breakpoint is hit and the suspend policy is
>>> SUSPEND_EVENT_THREAD. This is required for new tests to detect that
>>> command "stop thread at ..." is completed.
>>>
>>> Mach5 build and jdk_jdi tests succeeded.
>>>
>>> Webrev: http://cr.openjdk.java.net/~dtitov/8193879/webrev.01/
>>> Issue: https://bugs.openjdk.java.net/browse/JDK-8193879
>>>
>>> Thanks,
>>> --Daniil
>>>
>>>
>>>
>>
>
--- Begin Message ---
Hi Gary and Chris,
Please review an updated version of the patch that has newly added test for the
case when suspend policy is set to SUSPEND_EVENT_THREAD reimplemented using JDI
API. Thus, the changes in
src/jdk.jdi/share/classes/com/sun/tools/example/debug/tty/TTY.java are no
longer required.
I think vmInterrupted() is not invoked when suspend policy is set to
SUSPEND_EVENT_THREAD to address the case when different threads keep hitting
the same breakpoint and to avoid the switching the current thread in the
background.
The actual behavior of the debugger in the case when the breakpoint is hit and
suspend policy is set to SUSPEND_EVENT_THREAD is just to print "Breakpoint
hit:" in the output without adding any additional information or new line
character. After that you need to set the current thread by entering "thread"
command , e.g. "thread 1" and only then jdb prints the prompt (e.g. "main[1]")
. The behavior looks as confusing since it is not obvious for the user that
some input is expected from him (e.g. to set the current thread). I created a
separated issue for that at https://bugs.openjdk.java.net/browse/JDK-8211736 .
Webrev: http://cr.openjdk.java.net/~dtitov/8193879/webrev.02/
Issue: https://bugs.openjdk.java.net/browse/JDK-8193879
Thanks,
--Daniil
On 10/4/18, 10:28 AM, "Chris Plummer" <chris.plum...@oracle.com> wrote:
On 10/4/18 5:12 AM, Gary Adams wrote:
> In TTY.java do you need to force a simple prompt for the
> breakpoint event output? What prevents currentThread from
> being set at the time you are printing the prompt?
>
>
> 103 // Print the prompt if suspend policy is
> SUSPEND_EVENT_THREAD. In case of
> 104 // SUSPEND_ALL policy this is handled by vmInterrupted()
> method.
> 105 if (be.request().suspendPolicy() ==
> EventRequest.SUSPEND_EVENT_THREAD) {
> 106 MessageOutput.println();
> 107 MessageOutput.printPrompt();
Normally the thread is suspended after the above code is executed:
public void run() {
EventQueue queue = Env.vm().eventQueue();
while (connected) {
try {
EventSet eventSet = queue.remove();
boolean resumeStoppedApp = false;
EventIterator it = eventSet.eventIterator();
while (it.hasNext()) {
resumeStoppedApp |= !handleEvent(it.nextEvent());
<--- calls the modified code above
}
if (resumeStoppedApp) {
eventSet.resume();
} else if (eventSet.suspendPolicy() ==
EventRequest.SUSPEND_ALL) {
setCurrentThread(eventSet); <------
notifier.vmInterrupted();
}
However, it only calls setCurrentThread() for SUSPEND_ALL policies. So
what Daniil has done here is make it print a simple prompt if the policy
is SUSPEND_EVENT_THREAD. It's unclear to me what the actual debugger
behavior is in this case. Don't we still suspend and get a prompt from
which we can type in the next command? In this case, wouldn't you want a
full prompt? Related to that question, why is vmInterrupted() only
called if we suspend all threads, and not when we just suspend the
thread that the breakpoint came in on?
Chris
>
>
> In Jdb.java you allow the waiting for the simple prompt.
> I don't see waitForSimplePrompt used in any existing tests.
> Since it is only looking for a single character it could
> produce false positives if the '>' was produced in the
> output stream. Is this wait paired to the added prompt for the
> break point event?
>
> 236 return waitForSimplePrompt ? waitForSimplePrompt(1,
> cmd.allowExit) : waitForPrompt(1, cmd.allowExit);
>
> It might be a good idea to include a test with multiple
> threads each with a breakpoint that will trigger SUSPEND_EVENT_THREAD
> behavior.
>
> On 10/4/18, 12:29 AM, Daniil Titov wrote:
>> Please review the changes that fix the deadlock in the debugger when
>> the debugger is running with the tracing option on.
>>
>> The problem here is that when the tracing is on the "JDI Target VM
>> Interface" thread (the thread that reads all replies and then
>> notifies the thread that sent the request that the reply has been
>> received) is waiting for a lock which is already acquired by the
>> thread that sent the request and is waiting for reply.
>>
>> The fix itself is in
>> src/jdk.jdi/share/classes/com/sun/tools/jdi/VMState.java.
>>
>> The patch also reverts the changes done in 8129348 "Debugger hangs in
>> trace mode with TRACE_SENDS" in
>> src/jdk.jdi/share/classes/com/sun/tools/jdi/InvokableTypeImpl.java
>> since they address only a specific case (VM is suspended and static
>> method is invoked) while the proposed fix also solves issue 8129348
>> as well as issue 8193801 "Debugger hangs in trace mode for non-static
>> methods".
>>
>> The changes include new tests for issues 8193879, 8193801 and 8129348.
>>
>> The changes in
>> src/jdk.jdi/share/classes/com/sun/tools/example/debug/tty/TTY.java
>> solve the problem that the prompt is not printed in the debugger
>> output when the breakpoint is hit and the suspend policy is
>> SUSPEND_EVENT_THREAD. This is required for new tests to detect that
>> command "stop thread at ..." is completed.
>>
>> Mach5 build and jdk_jdi tests succeeded.
>>
>> Webrev: http://cr.openjdk.java.net/~dtitov/8193879/webrev.01/
>> Issue: https://bugs.openjdk.java.net/browse/JDK-8193879
>>
>> Thanks,
>> --Daniil
>>
>>
>>
>
--- End Message ---
