Thread-safety issue in cmake support ?

[Aleix Pol]

On Mon, Jun 7, 2010 at 9:28 PM, Andreas Pakulat <apaku at gmx.de> wrote:

> On 07.06.10 19:52:01, Aleix Pol wrote:
> > On Mon, Jun 7, 2010 at 7:40 PM, Milian Wolff <mail at milianw.de> wrote:
> >
> > > Christoph Cullmann, 07.06.2010:
> > > > On Monday 07 June 2010 18:57:27 Milian Wolff wrote:
> > > > > Christoph Cullmann, 07.06.2010:
> > > > > > On Monday 07 June 2010 18:34:42 Andreas Pakulat wrote:
> > > > > > > > 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...
> > > > > >
> > > > > > QSettings ist not thread-safe, only reentrant.
> > > > >
> > > > > Making the foreground lock look even better :)
> > > >
> > > > I can only second then Andreas, you will kill your multi-threading
> then
> > > > completly I guess :/
> > > >
> > > > Like the name, the BKL (either big kernel or big kdevelop lock), you
> will
> > > > get lock contention really fast I guess, didn't you already some
> > > profiling
> > > > work, showing that atm the lock contention is high?
> > > >
> > > > I don't know any solution for the locking problems beside the bkl,
> too,
> > > as
> > > > kdevelop just intermixes to much stuff without locking and with the
> gui,
> > > > but keep in mind: each event, each mouse move, anything will trigger
> the
> > > > locking of this lock and compete with all your background threads,
> which
> > > > compete with each other then, too.
> > >
> > > True, it's a sad world we live in :)
> > >
> > > If someone has a better idea, I'm all for it though :-) Until then,
> it's
> > > probably the only thing we can do.
> > >
> > > There are sadly too many tools out there which we must use that do not
> work
> > > in
> > > a multi threaded environment...
> >
> > why can't we just serialize KConfig accesses inside CMake plugin?
>
> Because its not the only one accessing kconfig. The problem actually
> happens mostly when one thread accesses the project config while the
> cmake plugin tries to do that too. So the only way to fix that is having
> 1 global mutex to lock a specific kconfig object (i.e. project config).
> This could be done by wrapping KConfig in a custom class that replicates
> some of KConfig's API but would mean adjusting all code that uses it and
> it would also mean loosing some things from the API (like fetching a
> config group and writing to it transparently).
>
> Andreas
>
> --
> Things will be bright in P.M.  A cop will shine a light in your face.
>
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>

Well then, I guess that the way to solve that for the moment is to move
these KConfig accesses to the project initialization.
That might speed up a little the parsing too.

Aleix
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