Hi Robbin,
Looks good to me.
Thanks,
Serguei
On 5/14/19 07:02, Robbin Ehn wrote:
Hi Dan,
Full:
http://cr.openjdk.java.net/~rehn/8223306/v3/webrev/index.html
Inc:
http://cr.openjdk.java.net/~rehn/8223306/v3/inc/webrev/index.html
On 2019-05-08 18:02, Daniel D. Daugherty wrote:
General comment - Please make sure to update all copyright years before
pushing this changeset.
Fixed.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/runtime/Threads.java
L46:
L47: private static AddressField threadsField;
L48: private static CIntegerField lengthField;
nit - please delete blank line on L46
nit - please reduce the space between type and variable names
(I have no preference if you still keep them aligned)
nit - Please delete blank line on L74.
Fixed.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/tools/PStack.java
old L203: Threads threads = VM.getVM().getThreads();
old L204: for (JavaThread cur = threads.first(); cur !=
null; cur = cur.next()) {
new L203: VM.getVM().getThreads().doJavaThreads((cur) -> {
In this case, you did a lambda conversion...
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/tools/StackTrace.java
old L75: for (JavaThread cur = threads.first(); cur
!= null; cur = cur.next(), i++) {
new L75: for (int k = 0; k <
threads.getNumberOfThreads(); k++) {
new L76: JavaThread cur =
threads.getJavaThreadAt(k);
In this case, you didn't do a lambda conversion...
I'm trying to grok a reason for the different styles...
Update: Is is maybe a control flow thing? (No, I don't know
much
about lambdas.) As in: Loops that "break" or early return
are
not amenable to conversion to a lambda... (just guessing)
I converted those where it was easy to see that the loop did not have
an early termination. Lambdas removed.
L74: int i = 1;
Not your bug, but I think that 'i' is not used.
Fixed.
This all looks good to me... so thumbs up!
Thanks.
I have some reservations about using lambdas in a debugging tool.
My personal philosophy about debugging tools is that they should
be built on the simplest/most stable technology to reduce the
chances of the more complicated technology failing during a debug
session. I hate it when my debugger crashes!
I removed all lambdas!
Thanks for looking at this, Robbin
That said, SA is pretty much standalone so use of lambdas in this
debugging tool shouldn't affect the JVM or core file being debugged.
Again, thumbs up!
Dan
/Robbin
On 2019-05-08 11:17, Robbin Ehn wrote:
Hi David,
I changed to normal for:
http://rehn-ws.se.oracle.com/cr_mirror/8223306/v2/webrev/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/CommandProcessor.java.sdiff.html
Full:
http://rehn-ws.se.oracle.com/cr_mirror/8223306/v2/webrev/
Inc:
http://rehn-ws.se.oracle.com/cr_mirror/8223306/v2/inc/webrev/
Passes t1-2
Thanks, Robbin
On 2019-05-07 09:47, David Holmes wrote:
Hi Robbin,
On 7/05/2019 4:50 pm, Robbin Ehn wrote:
Hi David,
On 5/7/19 12:40 AM, David Holmes wrote:
Hi Robbin,
I have a few concerns here.
First I can't see how you are actually integrating the SA with
the ThreadSMR. You've exposed the _java_thread_list for it to
iterate but IIRC that list can be updated when threads are
added/removed and I'm not seeing how the SA is left iterating a
valid list - we'd normally using a ThreadsListHandle for that ??
(I may need a refresher on how this list is actually maintained.)
The processes must be paused. If the processes would be running
the linked list is also broken since if we unlink and delete a
JavaThread and then later SA follows that _next pointer.
Ah good point. Thanks for clarifying.
The conversion from external iteration of the list (the for
loop) to internal iteration (passing a lambda to JavaThreadsDo)
is also problematic. First I'd be very wary about introducing
lambda expressions into the SA code - lambda drags in a lot of
supporting code that could have an impact on the way SA
functions. There are places where we have to avoid lambdas due
to bootstrapping/initialization issues and I think the SA may be
an area where we also want to keep the code extremely simple.
There are already several usages of lambdas in SA code, e.g.
LinuxDebuggerLocal.java. SA is not a core module, it's an
application, there is not a bootstrap issue or so.
Hmm okay. Lambda carries a lot of baggage. But if its already
being used ...
Second by using lambda's with internal iteration you've lost the
ability to terminate the iteration loop! In the existing code if
we have a return in the for-loop then we not only terminate the
loop but the enclosing method. With the lambda the "return" just
ends the current iteration and JavaThreadsDo will then continue
with the next thread - so we don't even terminate the iteration
let alone the method performing the iteration. So for places
were we want to process one thread, for example, we will
continue to iterate all remaining threads and just do nothing
with them. That's very inefficient.
That's why I only used the internal iteration where we didn't
have early returns.
src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/CommandProcessor.java
- original code:
1556 new Command("where", "where { -a | id }", false) {
1557 public void doit(Tokens t) {
...
1564 for (JavaThread thread = threads.first();
thread != null; thread = thread.next()) {
1565 ByteArrayOutputStream bos = new
ByteArrayOutputStream();
1566 thread.printThreadIDOn(new
PrintStream(bos));
1567 if (all ||
bos.toString().equals(name)) {
1568 out.println("Thread " +
bos.toString() + " Address: " + thread.getAddress());
...
1577 }
1578 if (!all) return;
That looks like an early return to me.
Cheers,
David
-----
Thanks, Robbin
Thanks,
David
On 6/05/2019 5:31 pm, Robbin Ehn wrote:
Hi, please review.
Old threads linked list remove and updated SA to use
ThreadsList array instead.
Issue:
https://bugs.openjdk.java.net/browse/JDK-8223306
Webrev:
http://cr.openjdk.java.net/~rehn/8223306/webrev/
Passes t1-3 (which includes SA tests).
Thanks, Robbin
