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8283555: G1: Concurrent mark accesses uninitialized BOT of closed archive regions #7923

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tschatzl
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@tschatzl tschatzl commented Mar 23, 2022

Hi all,

please review this change that fixes crashes occurring in the Loom repo because of missing initialization in the BOT of closed archive regions. This is a bug here too, just typically not occurring.

So during marking through the closed archive regions (for statistics mainly) it can happen that there are objects in these closed archive regions that are split into chunks. To get the start of the object that contains this chunk, we use the BOT.

Since it is not initialized for the closed archive regions G1 crashes as that call returns garbage.

The fix is to not only initialize open archive regions, but also closed archive regions.

The problem started with JDK-8264908 which means that there will be a JDK 18 backport.

Testing: failing test with Loom, GHA

Thanks,
Thomas


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  • JDK-8283555: G1: Concurrent mark accesses uninitialized BOT of closed archive regions

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bridgekeeper bot commented Mar 23, 2022

👋 Welcome back tschatzl! 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.

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openjdk bot commented Mar 23, 2022

@tschatzl The following label will be automatically applied to this pull request:

  • hotspot-runtime

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 pull request command.

@openjdk openjdk bot added the hotspot-runtime hotspot-runtime-dev@openjdk.org label Mar 23, 2022
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/label add hotspot-gc

@tschatzl tschatzl marked this pull request as ready for review March 23, 2022 15:58
@openjdk openjdk bot added the hotspot-gc hotspot-gc-dev@openjdk.org label Mar 23, 2022
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The hotspot-gc label was successfully added.

@openjdk openjdk bot added the rfr Pull request is ready for review label Mar 23, 2022
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mlbridge bot commented Mar 23, 2022

Webrevs

@@ -2330,6 +2330,10 @@ void FileMapInfo::fixup_mapped_heap_regions() {
"Null closed_heap_regions array with non-zero count");
G1CollectedHeap::heap()->fill_archive_regions(closed_heap_regions,
num_closed_heap_regions);
// G1 marking uses the BOT for object chunking; for this reason we need to
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It would be good to have a reference to the actual method/class name performing "object chunking" in the comment.

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openjdk bot commented Mar 23, 2022

@tschatzl 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 details.

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

8283555: G1: Concurrent mark accesses uninitialized BOT of closed archive regions

Reviewed-by: ayang, iwalulya

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 1 new commit pushed to the master branch:

  • 3e73a0b: 8283237: CallSite should be a sealed class

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@openjdk openjdk bot added the ready Pull request is ready to be integrated label Mar 23, 2022
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Lgtm!

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Thanks @albertnetymk @walulyai for your reviews
/integrate

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openjdk bot commented Mar 24, 2022

Going to push as commit 19f01ab.
Since your change was applied there have been 21 commits pushed to the master branch:

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot added the integrated Pull request has been integrated label Mar 24, 2022
@openjdk openjdk bot closed this Mar 24, 2022
@openjdk openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Mar 24, 2022
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openjdk bot commented Mar 24, 2022

@tschatzl Pushed as commit 19f01ab.

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

@tschatzl tschatzl deleted the submit/8283555-uninitialized-ca-region-bot branch April 6, 2022 10:11
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