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8262092: vmTestbase/nsk/jvmti/scenarios/hotswap/HS102/hs102t001/TestDescription.java SIGSEGV in memmove_ssse3 #3889

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@alexmenkov alexmenkov commented May 5, 2021

Class loading can happen on different threads, but HotSwap agent is not ready to this - classCount variable is used without any synchronization.
The fix adds synchronization for ClassFileLoadHook.


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  • JDK-8262092: vmTestbase/nsk/jvmti/scenarios/hotswap/HS102/hs102t001/TestDescription.java SIGSEGV in memmove_ssse3

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@bridgekeeper bridgekeeper bot commented May 5, 2021

👋 Welcome back amenkov! 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 openjdk bot added the rfr label May 5, 2021
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@alexmenkov The following label will be automatically applied to this pull request:

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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.

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@mlbridge mlbridge bot commented May 5, 2021

Webrevs

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@lmesnik lmesnik left a comment

Also, generic comment. There are other counters which might require synchronization, like CompiledMethodLoadEventsCount. Doesn't it makes sense to fix them also or file a new bug?

@@ -67,6 +67,8 @@ static char** names = NULL;
static jvmtiClassDefinition* old_class_def = NULL;
static jvmtiClassDefinition* new_class_def = NULL;
static int classCount = 0;
/* lock to access classCount */
static jrawMonitorID classLoadLock = NULL;
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@lmesnik lmesnik May 5, 2021

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I think it would simpler to use an atomic counter rather than monitors for this fix.

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@alexmenkov alexmenkov May 5, 2021

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Do you mean use atomic from STL?
I'm not sure it would be simpler as we need logic like "get the value, if the value is less than max_classes, increment it"

if (!NSK_JVMTI_VERIFY(jvmti_env->Allocate(class_data_len, (unsigned char**)
&old_class_def[classCount].class_bytes))) {
// use while instead of if to exit the block on error
while (classCount < max_classes) {
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Could you please explain why this while is executed only once. It is not obvious.

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I tried to explain it in the comment :)
it should be "if (classCount < max_classes)",
but inside the if we have return statements and we need to do cleanup (exit monitor).
So I used well-known pattern with 1-pass cycle (note that "return"s are replaced with "break"s)

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Offline discussion shown that I forgot to add break at the end of the cycle. Will fix

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@alexmenkov alexmenkov commented May 5, 2021

Also, generic comment. There are other counters which might require synchronization, like CompiledMethodLoadEventsCount. Doesn't it makes sense to fix them also or file a new bug?

The problem with classCount is it's used as an index in the arrays.
CompiledMethodLoadEventsCount is only incremented (but formally it should be synchronized too).
And looks like CompiledMethodLoadEventsCount is actually not used (I mean the values is not checked)

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lmesnik approved these changes May 6, 2021
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@sspitsyn sspitsyn left a comment

This looks good.
Thanks,
Serguei

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@openjdk openjdk bot commented May 7, 2021

@alexmenkov 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:

8262092: vmTestbase/nsk/jvmti/scenarios/hotswap/HS102/hs102t001/TestDescription.java SIGSEGV in memmove_ssse3

Reviewed-by: lmesnik, sspitsyn

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 23 new commits pushed to the master branch:

  • 36e5ad6: 8263236: runtime/os/TestTracePageSizes.java fails on old kernels
  • 0ca86da: 8266002: vmTestbase/nsk/jvmti/ClassPrepare/classprep001 should skip events for unexpected classes
  • 52f1db6: 8262002: java/lang/instrument/VerifyLocalVariableTableOnRetransformTest.sh failed with "TestCaseScaffoldException: DummyClassWithLVT did not match .class file"
  • 04f7112: 8266293: Key protection using PBEWithMD5AndDES fails with "java.security.InvalidAlgorithmParameterException: Salt must be 8 bytes long"
  • a90b33a: 8266573: Make sure blackholes are tagged for all JVMCI paths
  • 2dcbedf: 8266044: Nested class summary should show kind of class or interface
  • e840597: 8266460: java.io tests fail on null stream with upgraded jtreg/TestNG
  • fcedfc8: 8266579: Update test/jdk/java/lang/ProcessHandle/PermissionTest.java & test/jdk/java/sql/testng/util/TestPolicy.java
  • c665dba: 8266561: Remove Compile::_save_argument_registers
  • 47d4438: 8266426: ZHeapIteratorOopClosure does not handle native access properly
  • ... and 13 more: https://git.openjdk.java.net/jdk/compare/6018336fc5e93675482b92df76594712c238adda...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 May 7, 2021
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@alexmenkov alexmenkov commented May 10, 2021

/integrate

@openjdk openjdk bot closed this May 10, 2021
@openjdk openjdk bot added integrated and removed ready rfr labels May 10, 2021
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@openjdk openjdk bot commented May 10, 2021

@alexmenkov Since your change was applied there have been 65 commits pushed to the master branch:

  • 23446f1: 8265128: [REDO] Optimize Vector API slice and unslice operations
  • e5d3ee3: 8266802: Shenandoah: Round up region size to page size unconditionally
  • 8851cb6: 8266779: Use instead of ZERO_WIDTH_SPACE
  • 0cc7833: 8265208: [JEP-356] : SplittableRandom and SplittableGenerators - splits() methods does not throw NullPointerException when source is null
  • f78440a: 8266440: Shenandoah: TestReferenceShortcutCycle.java test failed on AArch64
  • de78431: 8241502: C2: Migrate x86_64.ad to MacroAssembler
  • c8b7447: 8266603: jpackage: Add missing copyright file in Java runtime .deb installers
  • c494efc: 8266774: System property values for stdout/err on Windows UTF-8
  • 25d99e5: 8266330: itableMethodEntry::initialize() asserts with archived old classes
  • 5d761fc: 8266796: Clean up the unnecessary code in the method UnsharedNameTable#fromUtf
  • ... and 55 more: https://git.openjdk.java.net/jdk/compare/6018336fc5e93675482b92df76594712c238adda...master

Your commit was automatically rebased without conflicts.

Pushed as commit 9713152.

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

@alexmenkov alexmenkov deleted the HotSwapSync branch May 10, 2021
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