JDK-8312394: [linux] SIGSEGV if kernel was built without hugepage support

[tstuefe]

Somewhat trivial fixes. Hugepage detection crashes on systems whose kernels have no support compiled in for them.

• check the result of opendir() before using
• don't scan for hugepages at all if we don't have a default hugepage.

---

Progress

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Issue

• JDK-8312394: [linux] SIGSEGV if kernel was built without hugepage support (Bug - P3)

Reviewers

• David Holmes (@dholmes-ora - Reviewer)
• Aleksey Shipilev (@shipilev - Reviewer)

Reviewing

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[mlbridge]

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• 00: Full (4b3b7041)

[dholmes-ora]

Seems reasonable. But does the logging output in print_on need updating to reflect this special case?

Thanks.

[openjdk]

@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:

8312394: [linux] SIGSEGV if kernel was built without hugepage support

Reviewed-by: dholmes, shade

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At the time when this comment was updated there had been 13 new commits pushed to the master branch:

• 3283328: 8311130: AArch64: Sync SVE related CPU features with VM options
• a742767: 8312246: NPE when HSDB visits bad oop
• 37c756a: 8305506: Add support for fractional values of SafepointTimeoutDelay
• dfe764e: 8309032: jpackage does not work for module projects unless --module-path is specified
• 61ab270: 8310835: Address gaps in -Xlint:serial checks
• 5d57b5c: 6983726: Reimplement MethodHandleProxies.asInterfaceInstance
• 71cac8c: 8311663: Additional refactoring of Locale tests to JUnit
• aa23fd9: 8311879: SA ClassWriter generates invalid invokedynamic code
• 6f66213: 8312014: [s390x] TestSigInfoInHsErrFile.java Failure
• b5b6f4e: 8312164: Refactor Arrays.hashCode for long, boolean, double, float, and Object arrays
• ... and 3 more: https://git.openjdk.org/jdk/compare/028068a655bb08e016e7a915c2b2f6abc1e480a0...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]

Thanks, David!

Seems reasonable. But does the logging output in print_on need updating to reflect this special case?

Yes. Tested on an ARM32 SBC.

Thanks.

[tstuefe]

Could I have a second review? I'd like to get this out of the door quickly.

[shipilev]

Looks reasonable.

[tstuefe]

Thanks @dholmes-ora and @shipilev.

/integrate

[openjdk]

Going to push as commit 94eb44b.
Since your change was applied there have been 13 commits pushed to the master branch:

• 3283328: 8311130: AArch64: Sync SVE related CPU features with VM options
• a742767: 8312246: NPE when HSDB visits bad oop
• 37c756a: 8305506: Add support for fractional values of SafepointTimeoutDelay
• dfe764e: 8309032: jpackage does not work for module projects unless --module-path is specified
• 61ab270: 8310835: Address gaps in -Xlint:serial checks
• 5d57b5c: 6983726: Reimplement MethodHandleProxies.asInterfaceInstance
• 71cac8c: 8311663: Additional refactoring of Locale tests to JUnit
• aa23fd9: 8311879: SA ClassWriter generates invalid invokedynamic code
• 6f66213: 8312014: [s390x] TestSigInfoInHsErrFile.java Failure
• b5b6f4e: 8312164: Refactor Arrays.hashCode for long, boolean, double, float, and Object arrays
• ... and 3 more: https://git.openjdk.org/jdk/compare/028068a655bb08e016e7a915c2b2f6abc1e480a0...master

Your commit was automatically rebased without conflicts.

[openjdk]

@tstuefe Pushed as commit 94eb44b.

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