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JDK-8280002: jmap -histo may leak stream #7078

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tstuefe
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@tstuefe tstuefe commented Jan 14, 2022

Very trivial fix to a handle/memory leak.

JDK-8215624 added parallel heap iteration to both jmap -histo and jcmd GC.class_histogram. When called with an explicit file and an invalid argument for number of threads, it leaks the file (bit of memory and a handle).

Reproduce with:

jmap -histo:parallel=notanumber,file=xx.txt

Can only be reproduced with jmap. jcmd is safe, arguments are handled correctly in shared code.


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https://git.openjdk.java.net/jdk/pull/7078.diff

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bridgekeeper bot commented Jan 14, 2022

👋 Welcome back stuefe! 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 openjdk bot added the rfr label Jan 14, 2022
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openjdk bot commented Jan 14, 2022

@tstuefe The following labels will be automatically applied to this pull request:

  • hotspot-runtime
  • serviceability

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

@openjdk openjdk bot added serviceability hotspot-runtime labels Jan 14, 2022
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mlbridge bot commented Jan 14, 2022

Webrevs

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shipilev commented Jan 14, 2022

This is not as trivial, AFAICS. Note that the existing code delete fs after checking if (os != NULL && os != out). Does it mean this patch can effectively delete out? Or can it call delete nullptr?

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tstuefe commented Jan 14, 2022

This is not as trivial, AFAICS. Note that the existing code delete fs after checking if (os != NULL && os != out). Does it mean this patch can effectively delete out?

Thanks for looking at this. No, it is safe.

fs is a temporary fileStream which may or may not be NULL. It is safe to delete it. The delete you mention could be moved out of the condition and it would still be fine. The condition is only really needed for the output which should only appear if you don't write to stdout.

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@shipilev shipilev left a comment

Okay then!

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openjdk bot commented Jan 14, 2022

@tstuefe 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:

8280002: jmap -histo may leak stream

Reviewed-by: shade, sspitsyn

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 11 new commits pushed to the master branch:

  • fb8fdc0: 8279990: (fs) Awkward verbiage in description of Files.createTempFile(Path,String,String,FileAttribute)
  • d9dd485: 8280019: Remove unused code from metaspace
  • cf283e2: 8279570: IGV: Add source/destination property for load and store nodes with an associated field
  • f180530: 8279918: Fix various doc typos
  • ac98b22: 8280028: [BACKOUT] Parallel: More precise boundary in ObjectStartArray::object_starts_in_range
  • 61b8944: 8278851: Correct signer logic for jars signed with multiple digestalgs
  • 35734ad: 8279545: Buffer overrun in reverse_words of sharedRuntime_x86_64.cpp:3517
  • e8f494c: 8279825: JFR: JFCModel shouldn't need FilePermission to read predefined .jfc files
  • 9f30ec1: 8278398: jwebserver: Add test to confirm maximum request time
  • dd76a28: 8280000: Remove unused CardTable::find_covering_region_containing
  • ... and 1 more: https://git.openjdk.java.net/jdk/compare/965c64bca713446e7e513170aa9138a8a5eec5de...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.

@openjdk openjdk bot added the ready label Jan 14, 2022
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tstuefe commented Jan 14, 2022

Okay then!

Thanks, Alexey!

After your concerns I consider this to be not trivial enough, so I wait for a second reviewer.

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@sspitsyn sspitsyn left a comment

Hi Thomas,
Nice catch.
Looks good to me.
Thanks,
Serguei

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tstuefe commented Jan 14, 2022

Thanks, @shipilev and @sspitsyn !

/integrate

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openjdk bot commented Jan 14, 2022

Going to push as commit c359c35.
Since your change was applied there have been 11 commits pushed to the master branch:

  • fb8fdc0: 8279990: (fs) Awkward verbiage in description of Files.createTempFile(Path,String,String,FileAttribute)
  • d9dd485: 8280019: Remove unused code from metaspace
  • cf283e2: 8279570: IGV: Add source/destination property for load and store nodes with an associated field
  • f180530: 8279918: Fix various doc typos
  • ac98b22: 8280028: [BACKOUT] Parallel: More precise boundary in ObjectStartArray::object_starts_in_range
  • 61b8944: 8278851: Correct signer logic for jars signed with multiple digestalgs
  • 35734ad: 8279545: Buffer overrun in reverse_words of sharedRuntime_x86_64.cpp:3517
  • e8f494c: 8279825: JFR: JFCModel shouldn't need FilePermission to read predefined .jfc files
  • 9f30ec1: 8278398: jwebserver: Add test to confirm maximum request time
  • dd76a28: 8280000: Remove unused CardTable::find_covering_region_containing
  • ... and 1 more: https://git.openjdk.java.net/jdk/compare/965c64bca713446e7e513170aa9138a8a5eec5de...master

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot added the integrated label Jan 14, 2022
@openjdk openjdk bot closed this Jan 14, 2022
@openjdk openjdk bot removed ready rfr labels Jan 14, 2022
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openjdk bot commented Jan 14, 2022

@tstuefe Pushed as commit c359c35.

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

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