8264908: Investigate adding BOT range check in G1BlockOffsetTablePart::block_at_or_preceding #4775

walulyai · 2021-07-14T09:26:32Z

Hi all,

Please review this cleanup change to add an assert to G1BlockOffsetTablePart::block_at_or_preceding. Additionally, remove code that attempts to read beyond the _next_offset_index threshold.

Testing: Tier 1-3

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Issue

JDK-8264908: Investigate adding BOT range check in G1BlockOffsetTablePart::block_at_or_preceding

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Albert Mingkun Yang (@albertnetymk - Committer)
Thomas Schatzl (@tschatzl - Reviewer)

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…precondition

bridgekeeper · 2021-07-14T09:27:56Z

👋 Welcome back iwalulya! 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 · 2021-07-14T09:30:30Z

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

hotspot-gc

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mlbridge · 2021-07-14T09:34:29Z

Webrevs

albertnetymk · 2021-07-14T12:27:08Z

Re if (addr >= _hr->bottom() && addr < _hr->top()) {, I don't think we ever pass addr outside [bottom, top), so I suggest restore the original code and change this to an assert in another PR.

walulyai · 2021-07-14T12:30:26Z

Re if (addr >= _hr->bottom() && addr < _hr->top()) {, I don't think we ever pass addr outside [bottom, top), so I suggest restore the original code and change this to an assert in another PR.

Thanks, will do that.

tschatzl · 2021-07-14T14:13:16Z

src/hotspot/share/gc/g1/g1BlockOffsetTable.inline.hpp

-  // "addr" is past the end, start at the last valid index.
-  index = MIN2(index, _next_offset_index - 1);
+  // We must make sure that the offset table entry we use is valid.
+  assert(index < _next_offset_index, "Precondition");


I feel a bit uneasy that the caller (block_start) allows more than the callee (values < _hr->end()), but this is probably the change that is supposed to be coming?
Looks good, but I would have preferred the original change or the upcoming change with some asserts included.

I can add the deferred change, instead of splitting it off into a separate PR.

the caller (block_start) allows more than the callee (values < _hr->end())

That path should never be taken, so I am not worried about. I suggested putting that in another PR since those assertions are not obvious from the current ticket title. Anyway, this is subjective.

@albertnetymk : I know. Still it seems something is missing to me, but that's subjective. Let's just defer it.

tschatzl · 2021-07-14T15:12:27Z

src/hotspot/share/gc/g1/g1BlockOffsetTable.inline.hpp

-  // "addr" is past the end, start at the last valid index.
-  index = MIN2(index, _next_offset_index - 1);
+  // We must make sure that the offset table entry we use is valid.
+  assert(index < _next_offset_index, "Precondition");


@albertnetymk : I know. Still it seems something is missing to me, but that's subjective. Let's just defer it.

openjdk · 2021-07-14T15:13:33Z

@walulyai 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:

8264908: Investigate adding BOT range check in G1BlockOffsetTablePart::block_at_or_preceding

Reviewed-by: ayang, tschatzl

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At the time when this comment was updated there had been 1 new commit pushed to the master branch:

357fe09: 8247351: [aarch64] NullPointerException during stack walking (clhsdb "where -a")

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walulyai · 2021-07-15T08:47:51Z

Thanks @albertnetymk and @tschatzl for the reviews!

/integrate

openjdk · 2021-07-15T08:49:36Z

Going to push as commit 99d7f9a.
Since your change was applied there have been 21 commits pushed to the master branch:

e92e2fd: 8270517: Add Zero support for LoongArch
7a89ffe: 8270014: Add scoped objects for g1 young gc verification and young gc internal timing
793d772: 8270475: Remove unused G1STWDrainQueueClosure
1ebd946: 8270333: -XX:+VerifyStringTableAtExit should not do linear search
04b73bc: 8269656: The test test/langtools/tools/javac/versions/Versions.java has duplicate test cycles
7c23491: 8269598: Regressions up to 5% on aarch64 seems due to JDK-8268858
7d0edb5: Merge
7b4d84c: 8270422: Test build/AbsPathsInImage.java fails after JDK-8259848
72db09b: 8266313: (JEP-356) - RandomGenerator spec implementation requirements tightly coupled to JDK internal classes
3bbd233: 8270075: SplittableRandom extends AbstractSplittableGenerator
... and 11 more: https://git.openjdk.java.net/jdk/compare/589a1d53df0f53c064fda8a2ac491e0a536ea487...master

Your commit was automatically rebased without conflicts.

openjdk · 2021-07-15T08:49:52Z

@walulyai Pushed as commit 99d7f9a.

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

refactor G1BlockOffsetTablePart::block_at_or_preceding to add assert …

ea6c0c3

…precondition

openjdk bot added the rfr Pull request is ready for review label Jul 14, 2021

openjdk bot added the hotspot-gc hotspot-gc-dev@openjdk.org label Jul 14, 2021

@albertnetymk suggested changes

1d71c8c

walulyai force-pushed the JDK-8264908_G1BlockOffsetTablePart_block_at_or_preceding branch from 96ff795 to 1d71c8c Compare July 14, 2021 12:41

albertnetymk approved these changes Jul 14, 2021

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tschatzl reviewed Jul 14, 2021

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tschatzl approved these changes Jul 14, 2021

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openjdk bot added the ready Pull request is ready to be integrated label Jul 14, 2021

openjdk bot closed this Jul 15, 2021

openjdk bot added integrated Pull request has been integrated and removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Jul 15, 2021

8264908: Investigate adding BOT range check in G1BlockOffsetTablePart::block_at_or_preceding #4775

8264908: Investigate adding BOT range check in G1BlockOffsetTablePart::block_at_or_preceding #4775

walulyai commented Jul 14, 2021 •

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tschatzl Jul 14, 2021

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openjdk bot commented Jul 14, 2021 •

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walulyai commented Jul 15, 2021

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openjdk bot commented Jul 15, 2021

8264908: Investigate adding BOT range check in G1BlockOffsetTablePart::block_at_or_preceding #4775

8264908: Investigate adding BOT range check in G1BlockOffsetTablePart::block_at_or_preceding #4775

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walulyai commented Jul 14, 2021 • edited by openjdk bot

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