Thread-safety issue in cmake support ?

[Andreas Pakulat]

On 07.06.10 12:40:20, Sandro Andrade wrote:
> On Mon, Jun 7, 2010 at 12:20 PM, Milian Wolff <mail at milianw.de> wrote:
> > Sandro Andrade, 07.06.2010:
> >> Hi there,
> >>
> >> I sent this issue some time ago regarding multiple access to KConfig
> >> and I've been told to ask kde-core-devel guys
> >> about KConfig thread safety. However, KConfig is neither thread-safe
> >> nor even reentrant:
> >>
> >> http://lists.zerezo.com/kde-devel/msg12619.html
> >> http://lists.kde.org/?l=kde-devel&m=118037451920733&w=2
> >>
> >> So I should take care of this. The problem raises from calling
> >> "buildSystemManager->includeDirectories(project_item)" from multiples
> >> threads. I need to obtain project's include directories but probably
> >> the concurrent execution of background parser is causing such a crash
> >> (see following backtrace).
> >
> > Either put a mutex into your plugin or directly into cmake - dunno. You should
> > investigate where the function is currently used (isn't that used somewhere in
> > the background parser? meaning from multiple threads?)
> 
> I'm afraid putting a mutex (actually it already exists) in plugin does not
> solves the problem since it cames from somewhere out of plugin scope.
> 
> I suspect any concurrent execution of buildsystem's methods which access
> KConfig (more specifically CMakeUtils methods) would produce such error
> (in this case, currentInstallDir - executed from plugin - against
> currentBuildDir - from some still unknown place).
> 
> Error occurs either in main thread or in plugin. When in main thread
> it raises from
> a slot execution which it turns call a method using introspection, making things
> difficult to investigate.
> 
> IMHO, a lock in CMakeUtils would be a possible solution.

Oh, or we could just drop KConfig usage and use QSettings for the project
files. After all we might have to get rid of kcm-usage for project-config
too. The only thing we'd loose is the ability to read from two files "at
the same time". But then again, maybe its even good that where stuff is
written is more explicit so we can more easily move things around...

Andreas

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