Review Request 125152: KBuildSycoca: replace dbus-based locking with a lock file.

[David Edmundson]

> On Sept. 11, 2015, 12:56 p.m., Albert Astals Cid wrote:
> > src/kbuildsycoca/kbuildsycoca.cpp, line 370
> > <https://git.reviewboard.kde.org/r/125152/diff/1/?file=402639#file402639line370>
> >
> >     .lock() calls scare me, this will block forever if say kbuildsycoca crashed, right?
> >     
> >     How do we recover from that? Will this also lock the UI when we move the sycoca creation to apps?

QLockFile writes a timestamp and PID  into the lockfile. This is checked when the next process checks the lock.


- David


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On Sept. 11, 2015, 7:23 a.m., David Faure wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/125152/
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> 
> (Updated Sept. 11, 2015, 7:23 a.m.)
> 
> 
> Review request for KDE Frameworks and Albert Astals Cid.
> 
> 
> Repository: kservice
> 
> 
> Description
> -------
> 
> This is a more traditional way to protect concurrent access to a file,
> and it will (more easily) allow to have one lock file per sycoca file
> when we have LANG and DIRS in the filename.
> 
> It doesn't exactly remove the dependency on DBus though, since we still
> use it for the notification after the rebuild.
> 
> As an additional improvement, if a process has to wait for another
> to rebuild sycoca, when it can finally get the lock file, it does a quick
> mtime check and if there were no additional changes compared to the
> time of the last check (as stored in ksycoca's global header) then there
> is nothing to do, we can do an early return.
> 
> 
> Diffs
> -----
> 
>   src/kbuildsycoca/kbuildsycoca.cpp 2a1c6b3e2ef2add82f710e1a18cf77028f437407 
>   src/kbuildsycoca/kbuildsycoca_main.cpp 5a0c0e8b47996750a1bf25139e1c21eb0392044b 
>   src/kbuildsycoca/kbuildsycoca_p.h 1be91bf21bb6908a63ffe6c156830838ed1ff429 
>   src/sycoca/ksycoca.h 9d8b21e3c0f08375bece923c4029b54617f04b7f 
>   src/sycoca/ksycoca.cpp 36718e3ee951df19494031f17dec29d1f4dd39c5 
>   src/sycoca/ksycoca_p.h 1a377e3586330a22cbcab507ea7d7f16d1563f13 
> 
> Diff: https://git.reviewboard.kde.org/r/125152/diff/
> 
> 
> Testing
> -------
> 
> Running "kbuildsycoca --noincremental &" 5 times in a row quickly, and watching the debug output, shows that only the first one rebuilds, all others wait (approx 1.5s) and then realize there is nothing more to do, and exit.
> 
> 
> Thanks,
> 
> David Faure
> 
>

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