Review Request 128762: qmljs: restructure duchain locking to prevent deadlocks

[Milian Wolff]

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many good stuff, but also some breakage. and the fact that kevin found an assertion makes me wonder: did you run with this patch in a build with assertions enabled?


languages/qmljs/codecompletion/tests/test_qmljscompletion.cpp (line 125)
<https://git.reviewboard.kde.org/r/128762/#comment66531>

    did you make sure that the code in here does the locking itself?



languages/qmljs/duchain/declarationbuilder.cpp (line 126)
<https://git.reviewboard.kde.org/r/128762/#comment66524>

    use ENSURE_CHAIN_NOT_LOCKED



languages/qmljs/duchain/declarationbuilder.cpp (line 179)
<https://git.reviewboard.kde.org/r/128762/#comment66525>

    maybe it would be a better idea to only unlock+relock in here?



languages/qmljs/duchain/declarationbuilder.cpp (line 201)
<https://git.reviewboard.kde.org/r/128762/#comment66532>

    further down in this patch you relock before closing the context. also above you do the same. so why is this not required here?



languages/qmljs/duchain/declarationbuilder.cpp (line 343)
<https://git.reviewboard.kde.org/r/128762/#comment66533>

    it's not safe to access the contents of argumentDecls without holding the lock.



languages/qmljs/duchain/declarationbuilder.cpp (line 361)
<https://git.reviewboard.kde.org/r/128762/#comment66534>

    this is now unsafe



languages/qmljs/duchain/declarationbuilder.cpp (line 367)
<https://git.reviewboard.kde.org/r/128762/#comment66535>

    also, repeatedly locking and unlocking the duchain for write in such a loop is probably a bad idea performance wise. simply locking it once and then doing the write operations in ~1ms or what it takes is going to be much better



languages/qmljs/duchain/declarationbuilder.cpp (line 433)
<https://git.reviewboard.kde.org/r/128762/#comment66536>

    unsafe now



languages/qmljs/duchain/declarationbuilder.cpp (line 519)
<https://git.reviewboard.kde.org/r/128762/#comment66537>

    is that function locking internally?



languages/qmljs/duchain/declarationbuilder.cpp (line 606)
<https://git.reviewboard.kde.org/r/128762/#comment66526>

    undo this change



languages/qmljs/duchain/declarationbuilder.cpp (line 623)
<https://git.reviewboard.kde.org/r/128762/#comment66527>

    simply move this out of the block



languages/qmljs/duchain/declarationbuilder.cpp (line 1475)
<https://git.reviewboard.kde.org/r/128762/#comment66530>

    this looks wrong. you are accessing the current context and the baseClassesSize etc. in the loop, so the duchain must be locked



languages/qmljs/duchain/expressionvisitor.cpp (line 41)
<https://git.reviewboard.kde.org/r/128762/#comment66528>

    use ENSURE_CHAIN_NOT_LOCKED



languages/qmljs/duchain/expressionvisitor.cpp (line 300)
<https://git.reviewboard.kde.org/r/128762/#comment66529>

    just to make sure: this function is safely accessing the context and handling the locking for the context internally?



languages/qmljs/duchain/frameworks/nodejs.cpp (line 92)
<https://git.reviewboard.kde.org/r/128762/#comment66542>

    dito



languages/qmljs/duchain/frameworks/nodejs.cpp (line 130)
<https://git.reviewboard.kde.org/r/128762/#comment66543>

    dito



languages/qmljs/duchain/helper.cpp (line 161)
<https://git.reviewboard.kde.org/r/128762/#comment66538>

    dito



languages/qmljs/duchain/helper.cpp (line 282)
<https://git.reviewboard.kde.org/r/128762/#comment66539>

    dito



languages/qmljs/duchain/parsesession.cpp (line 236)
<https://git.reviewboard.kde.org/r/128762/#comment66540>

    dito



languages/qmljs/duchain/parsesession.cpp (line 269)
<https://git.reviewboard.kde.org/r/128762/#comment66541>

    dito


- Milian Wolff


On Sept. 1, 2016, 8:22 p.m., Sven Brauch wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/128762/
> -----------------------------------------------------------
> 
> (Updated Sept. 1, 2016, 8:22 p.m.)
> 
> 
> Review request for KDevelop and Kevin Funk.
> 
> 
> Bugs: 367825
>     http://bugs.kde.org/show_bug.cgi?id=367825
> 
> 
> Repository: kdevelop
> 
> 
> Description
> -------
> 
> We _must not_ hold a duchain lock when contextOfFile() is called. That
> might try to add something to the background parser queue, which locks
> the background parser mutex; then both locks are held, which causes
> deadlocks.
> 
> 
> Diffs
> -----
> 
>   languages/qmljs/codecompletion/context.cpp 3a44f45 
>   languages/qmljs/codecompletion/tests/test_qmljscompletion.cpp b689418 
>   languages/qmljs/duchain/declarationbuilder.cpp fb0cb5d 
>   languages/qmljs/duchain/expressionvisitor.cpp 3b641f5 
>   languages/qmljs/duchain/frameworks/nodejs.cpp 41964e4 
>   languages/qmljs/duchain/helper.cpp e537103 
>   languages/qmljs/duchain/parsesession.cpp d1ad4a9 
> 
> Diff: https://git.reviewboard.kde.org/r/128762/diff/
> 
> 
> Testing
> -------
> 
> Opened some test project, no crashes, no freezes, and the (I think) reason for the freeze is gone.
> 
> 
> Thanks,
> 
> Sven Brauch
> 
>

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