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<div class="moz-cite-prefix">Hi Frederik,<br>
<br>
Will review this tomorrow.<br>
Sorry for the latency, was busy with other things.<br>
<br>
In general, I do not like the idea to skip the synchronization.<br>
Also, it is important to keep the information from JVMTI
consistent.<br>
The data returned by the
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getLoadedClasses and
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getClassLoaderClasses should match.<br>
We also need to make sure it is consistent with other info the
JVMTI provides.<br>
This requirement is not for improvement or simplification.<br>
<br>
But more tomorrow...<br>
<br>
Thanks,<br>
Serguei<br>
<br>
<br>
On 10/2/13 2:28 AM, Fredrik Arvidsson wrote:<br>
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<blockquote cite="mid:524BE733.2070205@oracle.com" type="cite">
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Hi and thanks for all your comments.<br>
<br>
I have simplified the code in <b>instanceKlass.cpp</b> like
suggested and here is a new webrev:<br>
<a moz-do-not-send="true"
href="http://cr.openjdk.java.net/%7Eallwin/farvidss/8024423/webrev.01/">http://cr.openjdk.java.net/~allwin/farvidss/8024423/webrev.01/</a><br>
<br>
Regarding the need to synchronize the access to
ClassLoaderDataGraph I have come to the conclusion that it should
be safe to call this without any additional synchronization since
newly loaded and added classes are appended to the end of its
'list' of classes. This would mean that the call could 'miss' the
classes added during the collection phase, but this is not a big
issue. I hope that my conclusion is correct.<br>
<br>
I believe that the
JvmtiGetLoadedClasses::getClassLoaderClasses(...) method is to be
left alone this time since I got the impression that only
SystemDictionary 'knows' about initiating class loaders.<br>
<br>
There is plenty of room for improvement and simplification of much
of the code in this area, but I feel that it must wait until
another time. The task to re-factor and simplify would quickly
grow out of hands I'm afraid :)<br>
<br>
Cheers<br>
/Fredrik<br>
<br>
<div class="moz-cite-prefix">On 2013-10-01 09:34, <a
moz-do-not-send="true" class="moz-txt-link-abbreviated"
href="mailto:serguei.spitsyn@oracle.com">serguei.spitsyn@oracle.com</a>
wrote:<br>
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<div class="moz-cite-prefix">Hi Frederik,<br>
<br>
<br>
Thank you for jumping on this issue!<br>
<br>
<br>
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<b>src/share/vm/oops/instanceKlass.cpp</b><br>
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<pre><span class="new">2333 int src_index = 0;</span>
2334 while (src_index < src_length) {
2335 dest[dest_index++] = src[src_index++];
2336 }
<span class="new">2337 </span>
<span class="new">2338 // If we have a hash, append it</span>
<span class="new">2339 if(hash_len > 0) {</span>
<span class="new">2340 int hash_index = 0;</span>
<span class="new">2341 while (hash_index < hash_len) {</span>
<span class="new">2342 dest[dest_index++] = hash_buf[hash_index++];</span>
<span class="new">2343 }</span>
<span class="new">2344 }
The above can be simplified a little bit:
// Add the actual class name
for (int src_index = 0; src_index < src_length; ) {
dest[dest_index++] = src[src_index++];
}
// If we have a hash, append it
for (int hash_index = 0; hash_index < hash_len; ) {
dest[dest_index++] = hash_buf[hash_index++];
}
The condition </span><span class="new">if(hash_len > 0)</span> is covered by the loop itself.
Style-related comments:
- <meta http-equiv="content-type" content="text/html; charset=ISO-8859-1"><span class="new">wrong indent at the lines: 2316</span>-2319
- need a space after the 'if' at the lines: 2315, 2339
<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1"><b>src/share/vm/prims/jvmtiGetLoadedClasses.cpp
</b>The copyright comment must be up-to-date.
The comments at the lines 35-38, 258-260 are not valid anymore.
> In this review I still have an outstanding unanswered question about
> the need to synchronize the access to the:
<span class="new" style="color: blue; font-weight: normal;">> ClassLoaderDataGraph::classes_do(&JvmtiGetLoadedClassesClosure::increment);
<font color="#000000">> and</font>
</span><span class="new" style="color: blue; font-weight: normal;">> ClassLoaderDataGraph::classes_do(&JvmtiGetLoadedClassesClosure::add);</span>
This kind of walking is usually done at safepoint in a VM_Operation.
You will find many examples in the jvmtiEnv.cpp, for instance, VM_GetAllStackTraces.
The suggestion from Mikael is good too.
Should this fix include the getClassLoaderClasses() as well?
I'm still trying to realize the impact and consistency of this fix. :(
What tests are you going to run for verification?
Thanks,
Serguei
<b>
</b>On 9/30/13 4:45 AM, Fredrik Arvidsson wrote:
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Hi<br>
<br>
Please help me to review the changes below:<br>
<br>
Jira case: <a moz-do-not-send="true"
href="https://bugs.openjdk.java.net/browse/JDK-8024423">https://bugs.openjdk.java.net/browse/JDK-8024423</a><br>
Webrev: <a moz-do-not-send="true"
href="http://cr.openjdk.java.net/%7Eallwin/farvidss/8024423/webrev.00/">http://cr.openjdk.java.net/~allwin/farvidss/8024423/webrev.00/</a><br>
<br>
In this review I still have an outstanding unanswered question
about the need to synchronize the access to the:<br>
<pre style="color: rgb(0, 0, 0); font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><span class="new" style="color: blue; font-weight: normal;">ClassLoaderDataGraph::classes_do(&JvmtiGetLoadedClassesClosure::increment);
<font color="#000000">and</font>
</span><span class="new" style="color: blue; font-weight: normal;">ClassLoaderDataGraph::classes_do(&JvmtiGetLoadedClassesClosure::add);</span>
calls in
<a moz-do-not-send="true" href="http://cr.openjdk.java.net/%7Eallwin/farvidss/8024423/webrev.00/src/share/vm/prims/jvmtiGetLoadedClasses.cpp.udiff.html">http://cr.openjdk.java.net/~allwin/farvidss/8024423/webrev.00/src/share/vm/prims/jvmtiGetLoadedClasses.cpp.udiff.html</a>
Please give me advise on this.
There will be a review soon regarding re-enabling the tests that failed because of the above bug, see:
<a moz-do-not-send="true" href="https://bugs.openjdk.java.net/browse/JDK-8025576">https://bugs.openjdk.java.net/browse/JDK-8025576</a>
Cheers
/Fredrik
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