8272756: Remove unnecessary explicit initialization of volatile variables in java.desktop #5197

stsypanov · 2021-08-20T09:41:15Z

This is a continuation of

As mentioned in JDK-6736490:

An explicit initialization of a volatile class instance variable, such as private volatile Object = null; or private volatile int scale = 0; is unnecessary since the Java spec automatically initializes objects to null and primitive type short, int, long, float and double to 0 and boolean to false. Explicit initialization of volatile variable to a value the same as the default implicit initialized value results in an unnecessary store and membar operation.

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JDK-8272756: Remove unnecessary explicit initialization of volatile variables in java.desktop

Reviewers

@turbanoff (no known github.com user name / role) ⚠️ Review applies to a3558d0
Jayathirth D V (@jayathirthrao - Reviewer)
Alexey Ivanov (@aivanov-jdk - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/5197/head:pull/5197
$ git checkout pull/5197

Update a local copy of the PR:
$ git checkout pull/5197
$ git pull https://git.openjdk.java.net/jdk pull/5197/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 5197

View PR using the GUI difftool:
$ git pr show -t 5197

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/5197.diff

…s in java.desktop

bridgekeeper · 2021-08-20T09:41:39Z

👋 Welcome back stsypanov! 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 · 2021-08-20T09:43:34Z

@stsypanov The following labels will be automatically applied to this pull request:

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awt
i18n
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mlbridge · 2021-08-20T09:48:35Z

Webrevs

mrserb · 2021-08-20T21:26:41Z

src/java.desktop/share/classes/com/sun/imageio/plugins/tiff/TIFFIFD.java

        Set<Integer> tags = essentialTags;
        if (tags == null) {
-            essentialTags = tags = Set.of(
+            essentialTags = Set.of(


What is the purpose of the local tags here?

Looks like there's no purpose, tags is not used after assignment

Maybe it's kind of a protection from a race. Yet it's possible either way: another thread could see essentialTags == null before this one initialises the field.

I think we can drop it completely.

I still suggest to remove the local tag completely.

@jayathirthrao @stsypanov Looks like this was not addressed? It will be good to include it in some future cleanup.

As far as I can see, it was. Line 64:

essentialTags = Set.of(

And it shows as such in the diff of the commit.

That was the usage of the local var, the current thread was about the local var itself, it is still there.

Good catch!
I missed that the local variable is still there and now it's unused, so an IDE should issue a warning about it.

turbanoff · 2021-09-20T11:55:43Z

As I can see there are a few more zero-initializations of volatiles. Are they intentionally skipped?

sun.lwawt.macosx.CPlatformEmbeddedFrame#screenX
sun.lwawt.macosx.CPlatformEmbeddedFrame#screenY
sun.lwawt.macosx.CWarningWindow#currentIcon
com.sun.media.sound.SoftSynthesizer.WeakAudioStream#silent_samples

…s in java.desktop

stsypanov · 2021-09-21T11:41:35Z

@turbanoff nice catch! I've missed them in my original commit, no intention here. I've included them either.

stsypanov · 2021-09-26T12:08:31Z

/integrate

openjdk · 2021-09-26T23:50:06Z

@stsypanov This PR has not yet been marked as ready for integration.

openjdk · 2021-10-08T07:39:51Z

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$ git checkout 8272756
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openjdk · 2021-10-08T07:39:55Z

@stsypanov 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:

8272756: Remove unnecessary explicit initialization of volatile variables in java.desktop

Reviewed-by: jdv, aivanov

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 153 new commits pushed to the master branch:

36b89a1: 8274785: ciReplay: Potential crash due to uninitialized Compile::_ilt variable
2aacd42: 8274145: C2: condition incorrectly made redundant with dominating main loop exit condition
6364719: 8274004: Change 'nonleaf' rank name
b60837a: 8272586: emit abstract machine code in hs-err logs
97ea9dd: 8274840: Update OS detection code to recognize Windows 11
8de7763: 8273152: Refactor CDS FileMapHeader loading code
920e707: 8274920: ProblemList 2 VectorAPI tests failing due to "assert(!vbox->is_Phi()) failed"
7de2cf8: 8273910: Redundant condition and assignment in java.net.URI
8ca0846: 8274407: (tz) Update Timezone Data to 2021c
4ab274a: 8274858: Remove unused dictionary_classes_do functions
... and 143 more: https://git.openjdk.java.net/jdk/compare/4838a2ca7c8e75b95c1c68ada7523e2a94815f45...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.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@jayathirthrao, @aivanov-jdk) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

stsypanov · 2021-10-08T15:54:03Z

/integrate

openjdk · 2021-10-08T15:55:44Z

@stsypanov
Your change (at version d13ca90) is now ready to be sponsored by a Committer.

jayathirthrao · 2021-10-08T15:57:17Z

/sponsor

openjdk · 2021-10-08T15:58:42Z

Going to push as commit ccbce10.
Since your change was applied there have been 153 commits pushed to the master branch:

36b89a1: 8274785: ciReplay: Potential crash due to uninitialized Compile::_ilt variable
2aacd42: 8274145: C2: condition incorrectly made redundant with dominating main loop exit condition
6364719: 8274004: Change 'nonleaf' rank name
b60837a: 8272586: emit abstract machine code in hs-err logs
97ea9dd: 8274840: Update OS detection code to recognize Windows 11
8de7763: 8273152: Refactor CDS FileMapHeader loading code
920e707: 8274920: ProblemList 2 VectorAPI tests failing due to "assert(!vbox->is_Phi()) failed"
7de2cf8: 8273910: Redundant condition and assignment in java.net.URI
8ca0846: 8274407: (tz) Update Timezone Data to 2021c
4ab274a: 8274858: Remove unused dictionary_classes_do functions
... and 143 more: https://git.openjdk.java.net/jdk/compare/4838a2ca7c8e75b95c1c68ada7523e2a94815f45...master

Your commit was automatically rebased without conflicts.

openjdk · 2021-10-08T15:59:03Z

@jayathirthrao @stsypanov Pushed as commit ccbce10.

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

8272756: Remove unnecessary explicit initialization of volatile field…

d06aff5

…s in java.desktop

openjdk bot added the rfr Pull request is ready for review label Aug 20, 2021

openjdk bot added 2d client-libs-dev@openjdk.org swing client-libs-dev@openjdk.org sound client-libs-dev@openjdk.org i18n i18n-dev@openjdk.org awt client-libs-dev@openjdk.org labels Aug 20, 2021

mrserb reviewed Aug 20, 2021

View reviewed changes

mrserb mentioned this pull request Sep 18, 2021

8273581: Change the mechanism by which JDK loads the platform-specific FontManager class #5517

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8272756: Remove unnecessary explicit initialization of volatile field…

a3558d0

…s in java.desktop

turbanoff approved these changes Sep 21, 2021

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Merge branch 'master' into 8272756

d13ca90

jayathirthrao approved these changes Oct 8, 2021

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openjdk bot added the ready Pull request is ready to be integrated label Oct 8, 2021

aivanov-jdk approved these changes Oct 8, 2021

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openjdk bot added the sponsor Pull request is ready to be sponsored label Oct 8, 2021

openjdk bot closed this Oct 8, 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 sponsor Pull request is ready to be sponsored labels Oct 8, 2021

stsypanov deleted the 8272756 branch October 8, 2021 16:00

8272756: Remove unnecessary explicit initialization of volatile variables in java.desktop #5197

8272756: Remove unnecessary explicit initialization of volatile variables in java.desktop #5197

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