Re: RFR - Changes to address CCC 8014135: Support for statically linked agents

serguei.spit...@oracle.com Mon, 05 Aug 2013 12:01:09 -0700

Bob,

I'm not waiting for any changes from Bill at the moment but stillreading the code.Sorry for the latency but it takes time as not everything is clear to meyet.


Thanks,
Serguei

On 8/5/13 10:59 AM, Bob Vandette wrote:

Serguei,

Are you ok with the webrev at this point or are you waiting for any changes 
from Bill?

I've asked Coleen to review the code since she's an official Reviewer but she'd 
like to make
sure the serviceability team is ok with the changes.

Bob.


On Aug 3, 2013, at 12:34 AM, serguei.spit...@oracle.com wrote:

On 8/2/13 8:11 PM, Bill Pittore wrote:

On 8/2/2013 9:12 PM, serguei.spit...@oracle.com wrote:

Hi Bill,

A couple of more questions.

webrev.01/jvmti.html

An agent L whose image has been combined with the VM *is defined* as 
/statically linked/
if and only if the agent exports a function called Agent_OnLoad_L.

A question to the above.
Are we going to allow to link a library dynamically if it exports both
the Agent_OnLoad and Agent_OnLoad_L functions?
It can be convenient if a library exports both Agent_OnLoad and Agent_OnLoad_L
as it can be linked statically or dynamically depending on the need without 
changes.

It would be nice but the problem is that you could only link one agent into the 
VM if it exported Agent_OnLoad. Otherwise there would be a symbol collision 
with the second agent you linked in that also had Agent_OnLoad. As an agent 
developer you will have to select one or the other at build time, either 
statically linked in or dynamic.

I did not want to use the Agent_OnLoad for statically linked agent.
Just wanted to say that the presence of the Agent_OnLoad_L must be ignored
if the agent is linked dynamically.
Maybe this rule needs to be clearly stated in the JVMTI spec.

You already added the following statement to the JVMTI spec:
If a /statically linked/ agent L exports a function called Agent_OnLoad_L and
  a function called Agent_OnLoad, the Agent_OnLoad function will be ignored.

Could we say it in a shorter form?:
If a /statically linked/ agent L exports a function called Agent_OnLoad,
  the Agent_OnLoad function will be ignored.

I believe I copied this from JNI static linking JEP.  If so, I'll probably 
leave it as is just for consistency with JNI static spec. JVM TI static linking 
spec is closely related to JNI static linking spec.

I see. Then it is Ok with me.

In this context would it be reasonable to add another statement:
If a /dynamically linked/ agent L exports a function called Agent_OnLoad_L,
  the Agent_OnLoad_L function will be ignored.

The same questions apply to the Agent_OnAttach and Agent_OnAttach_L entry 
points.

I'm out on vacation for a couple of weeks so I'll leave it up to Bob V. and 
yourself if you guys want to hash out better/different wording.

Thank you for the quick reply, and have a nice vacation!

Thanks,
Serguei

bill

Thanks,
Serguei


On 7/30/13 12:17 PM, bill.pitt...@oracle.com wrote:

Thanks Serguei for the comments. Some comments inline. I updated the webrevs at
http://cr.openjdk.java.net/~bpittore/8014135/jdk/webrev.02/
http://cr.openjdk.java.net/~bpittore/8014135/hotspot/webrev.01/

http://cr.openjdk.java.net/~bpittore/8014135/javadoc/index.html
http://cr.openjdk.java.net/~bpittore/8014135/hotspot/webrev.01/jvmti.html


On 7/26/2013 5:00 AM, serguei.spit...@oracle.com wrote:

Hi Bill,

Sorry for the big delay.


http://cr.openjdk.java.net/~bpittore/8014135/jdk/webrev.01/


src/share/classes/com/sun/tools/attach/VirtualMachine.java:


I'm suggesting to use the reference *<code>Agent_OnAttach[_L]</code>**||* even 
more consistently.
(If, in some cases, you prefer the longer form to underline the difference 
between
dynamically and statically linked libraries then feel free to leave it as it 
is.)

It would simplify the following fragments:

304      * It then causes the target VM to invoke the 
<code>Agent_OnAttach</code> function
305      * or, for a statically linked agent named 'L', the 
<code>Agent_OnAttach_L</code> function
   ==>

304      * It then causes the target VM to invoke the 
<code>Agent_OnAttach[_L]</code> function

409      * It then causes the target VM to invoke the 
<code>Agent_OnAttach</code>
410      * function or, for a statically linked agent named 'L', the
411      * <code>Agent_OnAttach_L</code> function as specified in the
  ==>
  409      * It then causes the target VM to invoke the 
<code>Agent_OnAttach[_L]</code>
  410      * function as specified in the

I left the above as is since it's part of the method description. The following 
fragments below I simplified as you suggested.

the following 4 identical fragments:

  341      *          If the <code>Agent_OnAttach</code> function returns an 
error
  342      *          or, for a statically linked agent named 'L', if the
  343      *          <code>Agent_OnAttach_L</code> function returns
  344      *          an error.
  375      *          If the <code>Agent_OnAttach</code> function returns an 
error
  376      *          or, for a statically linked agent named 'L', if the
  377      *          <code>Agent_OnAttach_L</code> function returns
  378      *          an error.
  442      *          If the <code>Agent_OnAttach</code> function returns an 
error
  443      *          or, for a statically linked agent named 'L', if the
  444      *          <code>Agent_OnAttach_L</code> function returns an error
  475      *          If the <code>Agent_OnAttach</code> function returns an 
error
  476      *          or, for a statically linked agent named 'L', if the
  477      *          <code>Agent_OnAttach_L</code> function returns
  478      *          an error.
  ==>

336      *          If the <code>Agent_OnAttach[_L]</code> function returns an 
error.


http://cr.openjdk.java.net/~bpittore/8014135/hotspot/webrev.00/


http://cr.openjdk.java.net/~bpittore/8014135/hotspot/webrev.00/jvmti.html
  src/share/vm/prims/jvmti.xml

Lines 442-462:  many extra <p/>'s. The fragment does not look well.
I'd suggest to remove most of them.
Also, these lines are too long. Could you make them shorter, please?
The same is applied to other long new lines in this file.

Cleaned this up a bit.

Lines 490-491, 502-503, 505-506:
     The same sentence is repeated 3 times: "the agent library may be statically 
linked ..."

490     Note that the agent library may be statically linked into the executable
491     in which case no actual loading takes place.

Fixed.

501 <code>-agentpath:c:\myLibs\foo.dll=opt1,opt2</code> is specified, the VM 
will attempt to
502         load the shared library <code>c:\myLibs\foo.dll</code>. As 
mentioned above, the agent library may be statically linked into the executable
503         in which case no actual loading takes place

505     Note that the agent library may be statically linked into the executable
506     in which case no actual loading takes place.

Tweaked the above a bit to make it less wordy.

Lines 677-678: The dot is missed at the end of line 677:

677     and enabled the event

Fixed.

src/os/posix/vm/os_posix.cpp

   - no comments

src/os/windows/vm/os_windows.cpp

   - no comments

src/share/vm/prims/jvmtiExport.cpp

   - no comments

src/share/vm/runtime/arguments.hpp

   - no comments

src/share/vm/runtime/os.cpp

Space is missed after the 'if':
   471     if(entryName != NULL) {

Fixed.

Extra space after the '*':
  483   void * saveHandle;

Fixed.

src/share/vm/runtime/os.hpp

   - no comments

src/share/vm/runtime/thread.cpp

  The line has been removed:
  3866         break;

Correct, the inner for loop was removed so no need for the break;

I'm still in process of reading the code.
Another pass is needed to make sure that nothing is missed.
But in general, the code quality is pretty good.

Thanks,
Serguei



On 7/25/13 10:47 AM, bill.pitt...@oracle.com wrote:

Still need an official reviewer for the hotspot changes for statically linked 
agents.

thanks,
bill

These changes address bug 8014135 which adds support for statically linked 
agents in the VM. This is a followup to the recent JNI spec changes that 
addressed statically linked JNI libraries( 8005716).
The JEP for this change is the same JEP as the JNI changes:
http://openjdk.java.net/jeps/178

Webrevs are here:

http://cr.openjdk.java.net/~bpittore/8014135/jdk/webrev.00/
http://cr.openjdk.java.net/~bpittore/8014135/hotspot/webrev.00/

The changes to jvmti.xml can also be seen in the output file that I placed here:
http://cr.openjdk.java.net/~bpittore/8014135/hotspot/webrev.00/jvmti.html

Thanks,
bill

Re: RFR - Changes to address CCC 8014135: Support for statically linked agents

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