8325437: Safepoint polling in monitor deflation can cause massive logs

[stefank]

If -Xlog:monitorinflation=debug is used and ObjectSynchronizer::chk_in_use_entry is called while monitor deflation is safepoint polled/blocked, we can have deflated monitors on the in-use list and we can get a huge number of lines stating:

[10.570s][debug][monitorinflation] WARNING: monitor=0x00007fa1004f8480: in-use monitor is deflated.

This comes from the following code:

void ObjectSynchronizer::chk_in_use_entry(ObjectMonitor* n, outputStream* out,
                                          int* error_cnt_p) {
  if (n->owner_is_DEFLATER_MARKER()) {
    // This should not happen, but if it does, it is not fatal.
    out->print_cr("WARNING: monitor=" INTPTR_FORMAT ": in-use monitor is "
                  "deflated.", p2i(n));
    return;
  }

There are tentative plans to rewrite the monitor deflation to unlink deflated monitors from the in-use list before the safepoint polls, but I'd like to suggest that we make an interim patch that deletes this warning.

---

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Issue

• JDK-8325437: Safepoint polling in monitor deflation can cause massive logs (Enhancement - P4)

Reviewers

• Axel Boldt-Christmas (@xmas92 - Reviewer)
• Daniel D. Daugherty (@dcubed-ojdk - Reviewer)
• Aleksey Shipilev (@shipilev - Reviewer)

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[bridgekeeper]

👋 Welcome back stefank! 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]

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[mlbridge]

Webrevs

• 01: Full - Incremental (2719c84a)
• 00: Full (c58cc6f8)

[xmas92]

Lgtm.

[openjdk]

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

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

8325437: Safepoint polling in monitor deflation can cause massive logs

Reviewed-by: aboldtch, dcubed, shade

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[stefank]

Tier1-3 passes on Linux.

[dcubed-ojdk]

Sorry, I forgot to finish my review yesterday.

This looks fine. This WARNING mesg was from an era when I was trying to
make sure that idle ObjectMonitors were cleaned up as much as possible.
While that was a useful exercise when we were hunting down async monitor
deflation bugs, we're no longer trying to religiously make sure that idle
ObjectMonitors are deflated. Instead we're focused on trying to avoid inflation
unless absolutely necessary.

[stefank]

Thanks for reviewing!

[shipilev]

Ouch. Looks good!

[shipilev]

Maybe you want to merge from latest master to get clean GHA run. It should contain the GHA fix: 3c91b59

[stefank]

Thanks, Aleksey for reviewing. GHA passes, so I'm integrating now.
/integrate

[openjdk]

Going to push as commit 52d4976.
Since your change was applied there have been 3 commits pushed to the master branch:

• 8b70b8d: 8325440: Confusing error reported for octal literals with wrong digits
• 5daf622: 8325309: Amend "Listeners and Threads" in AWTThreadIssues.html
• d165d12: 8325510: Serial: Remove redundant arg in non_clean_card_iterate

Your commit was automatically rebased without conflicts.

[openjdk]

@stefank Pushed as commit 52d4976.

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