[vlc-devel] [RFC 0/2] New executor API
remi at remlab.net
Thu Aug 27 18:06:28 CEST 2020
Le torstaina 27. elokuuta 2020, 18.50.29 EEST Romain Vimont a écrit :
> On Thu, Aug 27, 2020 at 05:47:49PM +0300, Rémi Denis-Courmont wrote:
> > Le torstaina 27. elokuuta 2020, 17.32.10 EEST Romain Vimont a écrit :
> > > Yes, but vlc_executor_Cancel() may "interrupt" the task at any time, so
> > > you have to handle it anyway (timeout or not).
> > That's never going to work, unless the runnable has its own killable
> > process (which should be had for other reasons, notably I/O scheduling).
> I don't understand why you say it can't work.
You simply can't stop another thread arbitrarily.
You can use thread cancellation, if the threaded code supports it - but most
likely it doesn't, and there is a lack of static analysis support to verify
basic cancellation mistakes.
Again, it's much much easier and less error-prone to have a time-out within
> Canceling a runnable does work. This is already what
> background_worker_Cancel() provides, and with the vlc_executor_t it
> calls the interrupt() callback:
Unless the runnable is trivial and spends all its time waiting on a single
"thing", it simply won't work.
It also won't work if the runnable is I/O bound, as there are no sane ways to
interrupt poll() in library code, even less read/recv and write/send
functions. You can cancel poll(), or you can send a thread signal, but
libraries have no ways to reserve a signal for their own use.
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