On 2020-04-01 12:22, Kevin Walls wrote:
Hi Coleen and all -
Given the choice I'd ask that we don't remove attach/detach because it
limits the scope of what a clhsdb can do in future. Commands like
jstack are a one-shot operation. A Tool like clhsdb is ideally more
flexible than that.
The SA is (I suggest) "too static" in its "there is one VM" approach,
so we can't write a Tool that attaches to multiple VMs. If we remove
attach/detach, it could not even gather information in a series of
requests. This is not going to be in the product any time soon, and
maybe never, but it doesn't look right that we cut off such experiments.
Removing the Observer, yes would imply making detach into detach and
exit. I think the clhsdb "attach" command would still work (once
only!) but is odd without detach (so do we make "bin/jhsdb clhsdb"
require parameters...).
It looks like this changes the direction of the Tools in order to
remove the deprecation warnings.
Magnus' webrev
http://cr.openjdk.java.net/~ihse/hotspot-agent-observer/webrev.01/
does add/duplicate some code, but I like it for keeping things working 8-)
Here's an updated version of that approach that minimizes the amount of
new code:
http://cr.openjdk.java.net/~ihse/hotspot-agent-observer/webrev.03
The difference is that I do not duplicate the classes themselves, I just
subclass them to get a single point where the @SuppressWarnings can be
put. The only change needed in the rest of the files is to make sure we
import these classes instead of the ones in java.util.
/Magnus
Thanks
Kevin
On 31/03/2020 22:20, coleen.phillim...@oracle.com wrote:
On 3/31/20 4:55 PM, Chris Plummer wrote:
On 3/31/20 1:32 PM, coleen.phillim...@oracle.com wrote:
On 3/31/20 12:19 PM, Poonam Parhar wrote:
Hello Coleen,
Does the removal of this code only impact the 'reattach'
functionality, and it does not affect any commands available in
'clhsdb' once it is attached to a core file? If that's true, then
I think it should be okay to remove this code.
Hi Poonam, Thank you for answering. Yes, this patch only removes
the reattach functionality. I tried out the other clhsdb commands
from your wiki page, and they worked fine, including object and
heap inspection.
I'm trying to understand exactly when all these static initializes
are triggered. Is it only after you do an attach?
The implementation of clhsdb reattach is exactly the same as doing a
detach followed by an attach to the same process. I'm not sure how
much value it has, but I think in general the removal of this code
means you can't detach and then attach to anything, even a different
pid. So "detach" might as well become "detach-and-exit", because
your clhsdb session is dead once you detach. Do we really want to do
this?
Well, that was my question. It seems like you could just exit and
start up jhsdb again and that's more like something someone would do
just as easily. Given the use cases that we've seen from sustaining,
this appears to be unneeded functionality.
The original mail was proposing adding more code to work around the
deprecation messages. It seems like more code should not be added
for something that is unused.
thanks,
Coleen
Chris
Thanks,
Coleen
Thanks,
Poonam
On 3/31/20 5:34 AM, coleen.phillim...@oracle.com wrote:
To answer my own question, this functionality is used to allow
detach/reattach from {cl}hsdb. Which seems to work on linux but
not windows with this code removed.
The next question is whether this is useful functionality to
justify all this code (900+ and this new code that Magnus has
added). Can't you just exit and restart the clhsdb process on
the core file or process?
For the record, this is me playing with python to remove this code.
http://cr.openjdk.java.net/~coleenp/2020/01/webrev/index.html
Thanks,
Coleen
On 3/30/20 3:04 PM, coleen.phillim...@oracle.com wrote:
I was wondering why this is needed when debugging a core file,
which is the key thing we need the SA for:
/** This is used by both the debugger and any runtime system.
It is
the basic mechanism by which classes which mimic
underlying VM
functionality cause themselves to be initialized. The given
observer will be notified (with arguments (null, null))
when the
VM is re-initialized, as well as when it registers itself
with
the VM. */
public static void registerVMInitializedObserver(Observer o) {
vmInitializedObservers.add(o);
o.update(null, null);
}
It seems like if it isn't needed, we shouldn't add these classes
and remove their use.
Coleen
On 3/30/20 8:14 AM, Magnus Ihse Bursie wrote:
No opinions on this?
/Magnus
On 2020-03-25 23:34, Magnus Ihse Bursie wrote:
Hi everyone,
As a follow-up to the ongoing review for JDK-8241618, I have
also looked at fixing the deprecation warnings in
jdk.hotspot.agent. These fall in three broad categories:
* Deprecation of the boxing type constructors (e.g. "new
Integer(42)").
* Deprecation of java.util.Observer and Observable.
* The rest (mostly Class.newInstance(), and a few number of
other odd deprecations)
The first category is trivial to fix. The last category need
some special discussion. But the overwhelming majority of
deprecation warnings come from the use of Observer and
Observable. This really dwarfs anything else, and needs to be
handled first, otherwise it's hard to even spot the other issues.
My analysis of the situation is that the deprecation of
Observer and Observable seems a bit harsh, from the PoV of
jdk.hotspot.agent. Sure, it might be limited, but I think it
does exactly what is needed here. So the migration suggested
in Observable (java.beans or java.util.concurrent) seems
overkill. If there are genuine threading issues at play here,
this assumption might be wrong, and then maybe going the
j.u.c. route is correct.
But if that's not, the main goal should be to stay with the
current implementation. One way to do this is to sprinkle the
code with @SuppressWarning. But I think a better way would be
to just implement our own Observer and Observable. After all,
the classes are trivial.
I've made a mock-up of this solution, were I just copied the
java.util.Observer and Observable, and removed the deprecation
annotations. The only thing needed for the rest of the code is
to make sure we import these; I've done this for three
arbitrarily selected classes just to show what the change
would typically look like. Here's the mock-up:
http://cr.openjdk.java.net/~ihse/hotspot-agent-observer/webrev.01
Let me know what you think.
/Magnus
