[vlc-devel] [RFC v2 1/2] executor: introduce new executor API

[Romain Vimont]

On Wed, Sep 02, 2020 at 11:43:54AM +0200, Steve Lhomme wrote:
> On 2020-09-02 11:38, Alexandre Janniaux wrote:
> > Hi,
> > 
> > On Wed, Sep 02, 2020 at 11:24:32AM +0200, Romain Vimont wrote:
> > > On Wed, Sep 02, 2020 at 10:34:28AM +0200, Romain Vimont wrote:
> > > > On Wed, Sep 02, 2020 at 08:13:15AM +0200, Steve Lhomme wrote:
> > > > > On 2020-09-01 18:13, Romain Vimont wrote:
> > > > > > +     *
> > > > > > +     * \param userdata the userdata provided to vlc_executor_Submit()
> > > > > > +     */
> > > > > > +    void (*run)(void *userdata);
> > > > > 
> > > > > Since the userdata is also part of the vlc_runnable, you may pass the
> > > > > vlc_runnable instead of the userdata. It allows more flexibilty in the
> > > > > future (for example if you want to do actions on the runnable, like run it
> > > > > again).
> > > > 
> > > > Good point. But now I realize that running a runnable again may cause
> > > > issues in regards to cancelation/deletion.
> > > 
> > > In fact, my preference is to pass "userdata" directly (not the
> > > vlc_runnable instance), because this is typically what the user directly
> > > need.
> > > 
> > > In case the very same runnable must be resubmitted (I would recommend
> > > against it, and create a new runnable instead, otherwise it may be more
> > > difficult to handle cancelation correctly), the runnable instance is
> > > typically accessible from the user-provided structure hidden behind the
> > > void*.
> > 
> > I agree, the task can queue a newer task while keeping the same state.
> 
> By the way, to be able to submit another runnable, you need to have access
> to the executor. You may pass it in the run() callback.

The user references whatever it wants in its userdata structure. If it
needs the executor, it will reference it from there, otherwise it won't.