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8283725: Launching java with "-Xlog:gc*=trace,safepoint*=trace,class*=trace" crashes the JVM #7978

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@dholmes-ora dholmes-ora commented Mar 28, 2022

I think the loop termination condition in LogOutput::update_config_string is not quite correct. We process "deviating tagsets" until there are no more - tracking n_deviants and n_selections. However, we can reach the case where n_deviants == 1 and there are no further selections possible - add_selections finds no more subsets for the given tagset. This causes the guarantee to fire as it expects to see selections as long as we still have deviations. We can fix this by adding a new check at the bottom of the loop:

    if (n_deviates == 1 && n_selections == 0) {
      // we're done as we couldn't reduce things any further
      break;
    }

I do not know what a "deviating tagset" means so it is unclear whether the bug is not checking for this "1 and 0" case, or whether the bug is that we got that final 0. Hopefully someone else may be able to expand on that.

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  • JDK-8283725: Launching java with "-Xlog:gc*=trace,safepoint*=trace,class*=trace" crashes the JVM

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👋 Welcome back dholmes! 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 28, 2022

@dholmes-ora 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 label Mar 28, 2022
@dholmes-ora dholmes-ora marked this pull request as ready for review Mar 28, 2022
@openjdk openjdk bot added the rfr label Mar 28, 2022
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Webrevs

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iklam commented Mar 30, 2022

The fix looks harmless. Since it fixes the immediate problem, I think we can integrate it.

However, it seems to me that the code is hard to understand. More comments (and perhaps refactoring/rewrite) would be beneficial in a separate RFE.

For example, there are many access to arrays without checking/asserting the range. These are quite worrying:

  size_t deviating_tagsets = LogTagSet::ntagsets() - max;
  ...
  const LogTagSet** deviates = NEW_C_HEAP_ARRAY(const LogTagSet*, deviating_tagsets, mtLogging);
  for (LogTagSet* ts = LogTagSet::first(); ts != NULL; ts = ts->next()) {
    LogLevelType level = ts->level_for(this);
    if (level == mcl) {
      continue;
    }
    deviates[n_deviates++] = ts;   //<<<<<< here

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iklam approved these changes Mar 30, 2022
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openjdk bot commented Mar 30, 2022

@dholmes-ora 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:

8283725: Launching java with "-Xlog:gc*=trace,safepoint*=trace,class*=trace" crashes the JVM

Reviewed-by: iklam, rehn

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 62 new commits pushed to the master branch:

  • e0a8669: 8281223: Improve the API documentation of HttpRequest.Builder::build to state that the default implementation provided by the JDK returns immutable objects.
  • eeca3a3: 8253569: javax.xml.catalog.Catalog.matchURI() implementation should reset state variables
  • ec0897a: 8281705: SourceLauncherTest.testSystemProperty isn't being run
  • 1ddab6f: 8283060: RawNativeLibraries should allow multiple clients to load/unload the same library
  • 835c7e8: 8283907: Fix Huawei copyright in various files
  • b8dd21b: 8283801: Cleanup confusing String.toString calls
  • ce27d9d: 8283494: Factor out calculation of actual number of XMM registers
  • e61ccfb: 8283470: Update java.lang.invoke.VarHandle to use sealed classes
  • e85fa2f: 8283700: Add final or sealed modifier to appropriate java.awt API classes
  • ec9ab55: 8282374: Java_sun_awt_X11_XlibWrapper_XSynchronize is wrong and unused
  • ... and 52 more: https://git.openjdk.java.net/jdk/compare/c2c0cb2a4372d78658326461562363de9a1a194f...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 Mar 30, 2022
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dholmes-ora commented Mar 30, 2022

Thanks for the review @iklam .

I think those array accesses are implicitly range-checked if you understand the invariants and relationships, but I agree it is non-obvious to the casual reader.

robehn
robehn approved these changes Mar 31, 2022
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@robehn robehn left a comment

Seems okay.

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dholmes-ora commented Mar 31, 2022

Thanks for the review @robehn

/integrate

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openjdk bot commented Mar 31, 2022

Going to push as commit 1ca0ede.
Since your change was applied there have been 64 commits pushed to the master branch:

  • c9a469a: 8283784: java_lang_String::as_platform_dependent_str stores to oop in native state
  • fbb8ca5: 8281717: Cover logout method for several LoginModule
  • e0a8669: 8281223: Improve the API documentation of HttpRequest.Builder::build to state that the default implementation provided by the JDK returns immutable objects.
  • eeca3a3: 8253569: javax.xml.catalog.Catalog.matchURI() implementation should reset state variables
  • ec0897a: 8281705: SourceLauncherTest.testSystemProperty isn't being run
  • 1ddab6f: 8283060: RawNativeLibraries should allow multiple clients to load/unload the same library
  • 835c7e8: 8283907: Fix Huawei copyright in various files
  • b8dd21b: 8283801: Cleanup confusing String.toString calls
  • ce27d9d: 8283494: Factor out calculation of actual number of XMM registers
  • e61ccfb: 8283470: Update java.lang.invoke.VarHandle to use sealed classes
  • ... and 54 more: https://git.openjdk.java.net/jdk/compare/c2c0cb2a4372d78658326461562363de9a1a194f...master

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot added the integrated label Mar 31, 2022
@openjdk openjdk bot closed this Mar 31, 2022
@openjdk openjdk bot removed ready rfr labels Mar 31, 2022
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openjdk bot commented Mar 31, 2022

@dholmes-ora Pushed as commit 1ca0ede.

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

@dholmes-ora dholmes-ora deleted the 8283725-xlog branch Mar 31, 2022
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