8251261: CDS dumping should not clear states in live classes #227

iklam · 2020-09-17T18:53:55Z

We had an issue when CDS dumped a static archive (java -Xshare:dump), it would call Klass::remove_unshareable_info() too early. In one of the test failures, ZGC was still scanning the heap and stepped on a class whose mirror has been removed.

The fix is to avoid modifying the states of the Java classes during -Xshare:dump. Instead, we call Klass::remove_unshareable_info() only on the copy of the classes which are written into the archive. It's safe to do so because these copies are visible only to the CDS dumping code. They aren't accessible by the GC or any other subsystems.

It turns out that we were already doing this for the dynamic archive. So I just generalized the code in dynamicArchive.cpp and moved it to archiveBuilder.cpp. So this PR is one step forward for JDK-8234693 Consolidate CDS static and dynamic archive dumping code.

I also fixed another case where we modify the global VM state -- I removed Universe::clear_basic_type_mirrors().

We are still modifying some global VM states (such as SystemDictionary::_well_known_klasses). They seem harmless now, but we might have to do more fixes in the future.

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Issue

JDK-8251261: CDS dumping should not clear states in live classes

Reviewers

Yumin Qi (@yminqi - Reviewer) ⚠️ Review applies to 964ae34
Calvin Cheung (@calvinccheung - Reviewer)

Download

$ git fetch https://git.openjdk.java.net/jdk pull/227/head:pull/227
$ git checkout pull/227

bridgekeeper · 2020-09-17T18:56:03Z

👋 Welcome back iklam! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2020-09-17T18:57:24Z

@iklam The following label will be automatically applied to this pull request: hotspot.

When this pull request is ready to be reviewed, an RFR email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label (add|remove) "label" command.

iklam · 2020-09-17T19:00:51Z

/label add hotspot-runtime
/label remove hotspot

openjdk · 2020-09-17T19:01:21Z

@iklam
The hotspot-runtime label was successfully added.

openjdk · 2020-09-17T19:01:45Z

@iklam
The hotspot label was successfully removed.

mlbridge · 2020-09-17T19:08:17Z

Webrevs

yminqi

Looks good to me.

openjdk · 2020-09-21T23:21:00Z

@iklam This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for more details.

After integration, the commit message for the final commit will be:

8251261: CDS dumping should not clear states in live classes

Reviewed-by: minqi, ccheung

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 14 new commits pushed to the master branch:

9ac162e: 8251999: remove usage of PropertyResolvingWrapper in vmTestbase/nsk/aod
527a309: 8252722: More Swing plaf APIs that rely on default constructors
3495c19: 8250855: Address reliance on default constructors in the Java 2D APIs
a9d0440: 8250859: Address reliance on default constructors in the Accessibility APIs
89c5e49: 8253500: [REDO] JDK-8253208 Move CDS related code to a separate class
bf442c5: 8253539: Remove unused JavaThread functions for set_last_Java_fp/pc
dd2c456: 8253583: java/util/StringJoiner tests failing on 32-bit VMs after JDK-8246697
b1e2f02: 8253524: C2: Refactor code that clones predicates during loop unswitching
c303fd5: 8253581: runtime/stringtable/StringTableCleaningTest.java fails on 32-bit platforms
f3ea0d3: 8252583: Clean up unused phi-to-copy degradation mechanism
... and 4 more: https://git.openjdk.java.net/jdk/compare/f765a7f513d8e6013026fc05677a3a2d16d2a217...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

calvinccheung · 2020-09-21T23:55:34Z

src/hotspot/share/memory/heapShared.cpp

@@ -398,8 +398,6 @@ void KlassSubGraphInfo::add_subgraph_object_klass(Klass* orig_k, Klass *relocate
      new(ResourceObj::C_HEAP, mtClass) GrowableArray<Klass*>(50, mtClass);
  }

-  assert(relocated_k->is_shared(), "must be a shared class");


Why is this assert removed?

The delete is reasonable since line 293 already assert that relocated_k is a relocated klass in shared region which must be shared class I think.

Klass::set_is_shared() is called in Klass::remove_unshareable_info(). This PR has moved the calls to remove_unshareable_info() to a later stage. So when this assert is executed, relocated_k->is_shared() is false.

In the new commit 03f7485 I've restored the assert and changed it to the following:

assert(ArchiveBuilder::singleton()->is_in_buffer_space(relocated_k), "must be a shared class");

…classes

calvinccheung

Looks good.

…classes

iklam · 2020-09-24T19:18:28Z

/integrate

openjdk · 2020-09-24T19:20:15Z

@iklam Since your change was applied there have been 14 commits pushed to the master branch:

9ac162e: 8251999: remove usage of PropertyResolvingWrapper in vmTestbase/nsk/aod
527a309: 8252722: More Swing plaf APIs that rely on default constructors
3495c19: 8250855: Address reliance on default constructors in the Java 2D APIs
a9d0440: 8250859: Address reliance on default constructors in the Accessibility APIs
89c5e49: 8253500: [REDO] JDK-8253208 Move CDS related code to a separate class
bf442c5: 8253539: Remove unused JavaThread functions for set_last_Java_fp/pc
dd2c456: 8253583: java/util/StringJoiner tests failing on 32-bit VMs after JDK-8246697
b1e2f02: 8253524: C2: Refactor code that clones predicates during loop unswitching
c303fd5: 8253581: runtime/stringtable/StringTableCleaningTest.java fails on 32-bit platforms
f3ea0d3: 8252583: Clean up unused phi-to-copy degradation mechanism
... and 4 more: https://git.openjdk.java.net/jdk/compare/f765a7f513d8e6013026fc05677a3a2d16d2a217...master

Your commit was automatically rebased without conflicts.

Pushed as commit 8b85c3a.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

8251261: CDS dumping should not clear states in live classes

964ae34

openjdk bot added the hotspot hotspot-dev@openjdk.org label Sep 17, 2020

openjdk bot added the hotspot-runtime hotspot-runtime-dev@openjdk.org label Sep 17, 2020

openjdk bot removed the hotspot hotspot-dev@openjdk.org label Sep 17, 2020

iklam marked this pull request as ready for review Sep 17, 2020

openjdk bot added the rfr Pull request is ready for review label Sep 17, 2020

yminqi approved these changes Sep 21, 2020

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openjdk bot added the ready Pull request is ready to be integrated label Sep 21, 2020

calvinccheung reviewed Sep 21, 2020

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iklam added 2 commits Sep 22, 2020

Merge branch 'master' into 8251261-cds-shouldnt-clear-states-of-live-…

5eb540c

…classes

restore assert for shared class

03f7485

calvinccheung approved these changes Sep 22, 2020

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iklam added 2 commits Sep 22, 2020

Merge branch 'master' into 8251261-cds-shouldnt-clear-states-of-live-…

bba8574

…classes

Merge branch 'master' into 8251261-cds-shouldnt-clear-states-of-live-…

a6029d9

…classes

calvinccheung approved these changes Sep 23, 2020

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openjdk bot closed this Sep 24, 2020

openjdk bot added integrated Pull request has been integrated and removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Sep 24, 2020

8251261: CDS dumping should not clear states in live classes #227

8251261: CDS dumping should not clear states in live classes #227

iklam commented Sep 17, 2020 •

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openjdk bot commented Sep 24, 2020

8251261: CDS dumping should not clear states in live classes #227

8251261: CDS dumping should not clear states in live classes #227

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iklam commented Sep 17, 2020 • edited by openjdk[bot] bot

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iklam commented Sep 17, 2020 •

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