When the VM_Operation is created, we could take a snapshot of the
thread_id of the caller, then use that later.
Or we could block the creating thread from fully exiting until the VM op
executes.
dl
On 2/19/2013 1:59 AM, Staffan Larsen wrote:
I don't like this solution since we are swallowing information that could
potentially be interesting (that a VMOperation happened). I think it's fine to
say that in the case of non-blocking VMOperations, the caller thread will be
undefined or set to 0. We could add that information to the event field
description in traceevents.xml so that it is documented.
/Staffan
On 19 feb 2013, at 10:47, Markus Grönlund <[email protected]> wrote:
Hi David,
Thanks for taking a look.
The original idea was to use thread id 0 as a signal for "Unknown Thread" or "no thread"
if you like - however, there is nothing actually enforcing this; it was more of an implicit assumption (and
to be honest, the only OS which I know for sure will never give a tid of 0 is Windows). I have tried to find
information if a 0 will ever be given out by pthreads and mach_t, but I mostly find info on "process
relative opaque id"...so it could be likely that a 0 is used as a valid tid here (probably unlikely but
still...)
Also, I see that the tracing output just happily gives out tid == 0 if I write it in as
suggested in webrev01...I am not entirely happy with this. If we view 0 as "Unknown
Thread", this should maybe be treated differently.
I don't know yet what Id I will be able to use here to signal the fact that
thread is unknown (in a platform agnostic way) - but I will try to come up with
something.
In the interim, we should just avoid committing the event for non-concurrent VM
operations event altogether (I have mostly seen these as EnableBiasLocking and
Thread.Stop's).
The updated webrev02 gives a suggestion on only committing the tracing event
for non-concurrent vm ops:
http://cr.openjdk.java.net/~mgronlun/8007147/webrev02/
(follow up work will also need rework the event fields).
Thanks
Markus
-----Original Message-----
From: David Holmes
Sent: den 18 februari 2013 05:06
To: Markus Grönlund
Cc: [email protected]; [email protected]
Subject: Re: RFR(XXS): 8007147: Trace event ExecuteVMOperation may get dangling
pointer
Hi Markus,
So is zero as a thread id defined to mean "no thread" ?
David
On 13/02/2013 12:03 AM, Markus Grönlund wrote:
Greetings,
Kindly asking for reviews and a putback sponsorship for the following
change:
Bugid: http://bugs.sun.com/view_bug.do?bug_id=8007147
Webrev: http://cr.openjdk.java.net/~mgronlun/8007147/webrev01/
Please also note this is for hs24.
Thanks to David Holmes for pointing out this problem.
Thanks
Markus
