8325372: Shenandoah: SIGSEGV crash in unnecessary_acquire due to LoadStore split through phi #17926

rwestrel · 2024-02-20T09:46:31Z

After shenandoah barrier expansion, a shenandoah specific pass looks
for heap stable checks that are back to back:

if (heap_stable) {
  // fast path 1
} else {
  // slow path 1
}
if (heap_stable) {
  // fast path 2
} else {
  // slow path 2
}

and fuse them:

if (heap_stable) {
  // fast path 1
  // fast path 2
} else {
  // slow path 1
  // slow path 2
}

In the case of the failure, a GetAndSetP (or GetAndSetN) node is
between the 2 heap_stable checks. The fusion of the 2 tests is
implemented by taking advantage of the split if c2 optimization. But
split if doesn't support having a GetAndSet node at the region where
split if happens (that can only happen with shenandoah late barrier
expansion). That causes the GetAndSet node to lose its SCMemProj
which can then result in the GetAndSet being entirely removed.

The fix I propose is to not perform the heap_stable fusion in this
particular case.

/cc hotspot-compiler,shenandoah

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Issue

JDK-8325372: Shenandoah: SIGSEGV crash in unnecessary_acquire due to LoadStore split through phi (Bug - P4)

Reviewers

Aleksey Shipilev (@shipilev - Reviewer)
Roman Kennke (@rkennke - Reviewer)
Tobias Hartmann (@TobiHartmann - Reviewer)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/17926/head:pull/17926
$ git checkout pull/17926

Update a local copy of the PR:
$ git checkout pull/17926
$ git pull https://git.openjdk.org/jdk.git pull/17926/head

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$ git pr checkout 17926

View PR using the GUI difftool:
$ git pr show -t 17926

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https://git.openjdk.org/jdk/pull/17926.diff

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bridgekeeper · 2024-02-20T09:46:56Z

👋 Welcome back roland! 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 · 2024-02-20T09:48:13Z

@rwestrel
The hotspot-compiler label was successfully added.

The shenandoah label was successfully added.

mlbridge · 2024-02-20T09:58:02Z

Webrevs

01: Full - Incremental (cb1ace1b)
00: Full (6866a5ee)

shipilev

I suggest we rename the bug to:

8325372: Shenandoah: SIGSEGV crash in unnecessary_acquire due to LoadStore split through phi

shipilev · 2024-02-20T11:49:27Z

src/hotspot/share/gc/shenandoah/c2/shenandoahSupport.cpp

@@ -1734,11 +1734,26 @@ bool ShenandoahBarrierC2Support::identical_backtoback_ifs(Node* n, PhaseIdealLoo
  return true;
 }

+bool ShenandoahBarrierC2Support::merge_point_safe(Node* region) {


This should probably be is_merge_point_safe, since it answers bool?

There's an existing merge_point_safe method that validate merge points for split if (loopopts.cpp). That's why I named it like that.

Ah, okay then!

test/hotspot/jtreg/gc/shenandoah/compiler/TestUnsafeLoadStoreMergedHeapStableTests.java

…ergedHeapStableTests.java Co-authored-by: Aleksey Shipilëv <shipilev@amazon.de>

openjdk · 2024-02-20T15:30:55Z

@rwestrel 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:

8325372: Shenandoah: SIGSEGV crash in unnecessary_acquire due to LoadStore split through phi

Reviewed-by: shade, rkennke, thartmann

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 130 new commits pushed to the master branch:

c4409ea: 8325994: JFR: Examples in JFR.start help use incorrect separator
54f09d7: 8278527: java/util/concurrent/tck/JSR166TestCase.java fails nanoTime test
00ffc42: 8318761: MessageFormat pattern support for CompactNumberFormat, ListFormat, and DateTimeFormatter
d695af8: 8326376: java -version failed with CONF=fastdebug -XX:InitialCodeCacheSize=1024K -XX:ReservedCodeCacheSize=1200k
9f9a732: 8325752: Remove badMetaWordVal
864cf22: 8325742: Remove MetaWord usage from MemRegion
8e5c0ee: 8324832: JFR: Improve sorting of 'jfr summary'
724a2a2: 8321192: j.a.PrintJob/ImageTest/ImageTest.java: Fail or skip the test if there's no printer
f365d80: 8325153: SEGV in stackChunkOopDesc::derelativize_address(int)
4406915: 8323274: C2: array load may float above range check
... and 120 more: https://git.openjdk.org/jdk/compare/7cd25ed605469e3946a204b7b18d975c9768f2df...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.

rkennke

Looks good to me, thank you!
Roman

TobiHartmann

Shared code changes look good. Testing passed.

rwestrel · 2024-02-23T10:08:06Z

@shipilev @rkennke @TobiHartmann thanks for the reviews

rwestrel · 2024-02-23T10:08:11Z

/integrate

openjdk · 2024-02-23T10:09:08Z

Going to push as commit 5d414da.
Since your change was applied there have been 133 commits pushed to the master branch:

93a2e77: 8326129: Java Record Pattern Match leads to infinite loop
336bbbe: 8139457: Relax alignment of array elements
cb809f8: 8325215: Incorrect not exhaustive switch error
c4409ea: 8325994: JFR: Examples in JFR.start help use incorrect separator
54f09d7: 8278527: java/util/concurrent/tck/JSR166TestCase.java fails nanoTime test
00ffc42: 8318761: MessageFormat pattern support for CompactNumberFormat, ListFormat, and DateTimeFormatter
d695af8: 8326376: java -version failed with CONF=fastdebug -XX:InitialCodeCacheSize=1024K -XX:ReservedCodeCacheSize=1200k
9f9a732: 8325752: Remove badMetaWordVal
864cf22: 8325742: Remove MetaWord usage from MemRegion
8e5c0ee: 8324832: JFR: Improve sorting of 'jfr summary'
... and 123 more: https://git.openjdk.org/jdk/compare/7cd25ed605469e3946a204b7b18d975c9768f2df...master

Your commit was automatically rebased without conflicts.

openjdk · 2024-02-23T10:09:14Z

@rwestrel Pushed as commit 5d414da.

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

rwestrel added 2 commits February 19, 2024 17:27

test

2383cfc

fix

0e302e0

openjdk bot added hotspot-compiler hotspot-compiler-dev@openjdk.org shenandoah shenandoah-dev@openjdk.org labels Feb 20, 2024

test clean up

6866a5e

openjdk bot added the rfr Pull request is ready for review label Feb 20, 2024

shipilev reviewed Feb 20, 2024

View reviewed changes

Update test/hotspot/jtreg/gc/shenandoah/compiler/TestUnsafeLoadStoreM…

cb1ace1

…ergedHeapStableTests.java Co-authored-by: Aleksey Shipilëv <shipilev@amazon.de>

rwestrel changed the title ~~8325372: C2 compilation event causes SIGSEV crash (unnecessary_acquire(Node const*)) in JDK 17.0.x~~ 8325372: Shenandoah: SIGSEGV crash in unnecessary_acquire due to LoadStore split through phi Feb 20, 2024

shipilev approved these changes Feb 20, 2024

View reviewed changes

openjdk bot added the ready Pull request is ready to be integrated label Feb 20, 2024

timothyg-stripe mentioned this pull request Feb 20, 2024

JVM dying with unnecessary_acquire error corretto/corretto-17#93

Closed

rkennke approved these changes Feb 22, 2024

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TobiHartmann approved these changes Feb 23, 2024

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openjdk bot added the integrated Pull request has been integrated label Feb 23, 2024

openjdk bot closed this Feb 23, 2024

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Feb 23, 2024

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