JDK-8283670: gtest os.release_multi_mappings_vm is still racy #7953

tstuefe · 2022-03-25T06:01:19Z

JDK-8280940 fixed up os.release_multi_mappings_vm to make its handling of multiple neighboring reservations less racy, but I forgot to fix up the reserve_multiple() function, which follows the same pattern and is still racy. It reserves an area, releases it, then re-reserves stripes in that area.

We see intermittent problems on Linux PPC. This makes sense because we have here 64k pages, and therefore the stripe size is large, and we have a higher chance of someone grabbing that address space concurrently between the release and the stripe-wise re-reserve.

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Issue

JDK-8283670: gtest os.release_multi_mappings_vm is still racy

Reviewers

Martin Doerr (@TheRealMDoerr - Reviewer) ⚠️ Review applies to 669cb5d
David Holmes (@dholmes-ora - Reviewer) ⚠️ Review applies to 669cb5d

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bridgekeeper · 2022-03-25T06:02:23Z

👋 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 · 2022-03-25T06:04:24Z

@tstuefe 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.

mlbridge · 2022-03-26T07:59:05Z

Webrevs

01: Full - Incremental (6846a4e9)
00: Full (669cb5d3)

TheRealMDoerr

LGTM.

openjdk · 2022-03-28T13:29:44Z

@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:

8283670: gtest os.release_multi_mappings_vm is still racy

Reviewed-by: mdoerr, dholmes

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 45 new commits pushed to the master branch:

f01cce2: 8264160: Regex \b is not consistent with \w without UNICODE_CHARACTER_CLASS
634800a: 8283806: [BACKOUT] JDK 19 L10n resource files update - msgdrop 10
9b49900: 8283603: Remove redundant qualifier in Windows specific Attach Operation
d8fd222: 8282538: PKCS11 tests fail on CentOS Stream 9
d472c01: 8283711: Remove redundant 'new String' calls after concatenation
c0aecd1: 8280400: JDK 19 L10n resource files update - msgdrop 10
f0282d7: 8279488: ProcessBuilder inherits contextClassLoader when spawning a process reaper thread
a577656: 8282943: Unused weird key in compiler.properties
7f2a3ca: 8281561: Disable http DIGEST mechanism with MD5 and SHA-1 by default
0c472c8: 8283756: (zipfs) ZipFSOutputStreamTest.testOutputStream should only check inflated bytes
... and 35 more: https://git.openjdk.java.net/jdk/compare/2c43ecb43fa3c94b69478039f1cd70ed4a577768...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.

tstuefe · 2022-03-29T05:37:43Z

LGTM.

Thank you Martin!

Could I have a second review to get this on its way?

dholmes-ora

Looks good. One minor nit below.

dholmes-ora · 2022-03-29T05:56:32Z

test/hotspot/gtest/runtime/test_os.cpp

+      if (q == NULL) {
+        // Someone grabbed that area concurrently. Cleanup, then retry.
+        tty->print_cr("reserve_multiple: retry (%d)...", stripe);
+        if (stripe > 0) {


Nit: you don't need to check this as carefully_release_multiple is a no-op for num_stripes==0.

tstuefe · 2022-03-29T07:07:28Z

Thanks @dholmes-ora.

/integrate

openjdk · 2022-03-29T07:09:40Z

Going to push as commit 2e9fd56.
Since your change was applied there have been 45 commits pushed to the master branch:

f01cce2: 8264160: Regex \b is not consistent with \w without UNICODE_CHARACTER_CLASS
634800a: 8283806: [BACKOUT] JDK 19 L10n resource files update - msgdrop 10
9b49900: 8283603: Remove redundant qualifier in Windows specific Attach Operation
d8fd222: 8282538: PKCS11 tests fail on CentOS Stream 9
d472c01: 8283711: Remove redundant 'new String' calls after concatenation
c0aecd1: 8280400: JDK 19 L10n resource files update - msgdrop 10
f0282d7: 8279488: ProcessBuilder inherits contextClassLoader when spawning a process reaper thread
a577656: 8282943: Unused weird key in compiler.properties
7f2a3ca: 8281561: Disable http DIGEST mechanism with MD5 and SHA-1 by default
0c472c8: 8283756: (zipfs) ZipFSOutputStreamTest.testOutputStream should only check inflated bytes
... and 35 more: https://git.openjdk.java.net/jdk/compare/2c43ecb43fa3c94b69478039f1cd70ed4a577768...master

Your commit was automatically rebased without conflicts.

openjdk · 2022-03-29T07:10:00Z

@tstuefe Pushed as commit 2e9fd56.

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

JDK-8283670-os.release_multi_mappings_vm-is-still-racy

669cb5d

openjdk bot added the hotspot-runtime hotspot-runtime-dev@openjdk.org label Mar 25, 2022

tstuefe marked this pull request as ready for review March 26, 2022 07:53

openjdk bot added the rfr Pull request is ready for review label Mar 26, 2022

TheRealMDoerr approved these changes Mar 28, 2022

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openjdk bot added the ready Pull request is ready to be integrated label Mar 28, 2022

dholmes-ora approved these changes Mar 29, 2022

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6846a4e

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openjdk bot closed this Mar 29, 2022

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