On 6/19/06, Vlad Georgescu <vgeorgescu@gmail.com> wrote:
> On 6/19/06, Garrett Rooney <rooneg@electricjellyfish.net> wrote:
> > On 6/17/06, Vlad Georgescu <vgeorgescu@gmail.com> wrote:
> > > Also, how do we make sure that sasl_{client,server}_init() is only
> > > called once? I dug up this thread from the archives:
> > >
> > > http://svn.haxx.se/dev/archive-2003-05/2224.shtml
> > >
> > > Is there a solution for this?
> >
> > Well, it really depends on how correct we want to be. We can't be
> > 100% correct, since we can't rely on users of the Subversion libraries
> > calling an initialize function, since we didn't have one in Subversion
> > 1.0, and thus we can't introduce that requirement now. We can add a
> > new initialization function and request that people call it, but we
> > still need to work even if it wasn't called. Perhaps making the
> > current sasl init function you've got public, but inserting extra
> > calls to it in ra_svn before we make use of sasl code, just in case...
> >
> > For other examples of this sort of thing, see svn_utf_initialize,
> > although that's not really the same thing, since without it we still
> > work, we just work more slowly. Also svn_fs_initialize().
>
> I just realized APR has an atomic compare-and-swap function. So
> something along the lines of:
>
> static volatile apr_uint32_t init_started = 0, init_finished = 0;
>
> if (! apr_atomic_cas32(&init_started, 1, 0))
> {
> /* do initialization stuff */
> init_finished = 1;
> }
> else
> while (! init_finished)
> ;
>
> .. should do the trick.
That's a way to go, although be aware that the atomics code in APR
changed between APR 0.9.x and APR 1.x, so you'll have to make sure
your code works with both...
-garrett
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Received on Mon Jun 19 19:21:06 2006