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

[David Faure]

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https://git.reviewboard.kde.org/r/125152/
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Review request for KDE Frameworks and Albert Astals Cid.


Repository: kservice


Description
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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
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  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
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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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