Re: [libgpiod v2][PATCH] treewide: allow polling functions to block indefinitely

[Bartosz Golaszewski <brgl@xxxxxxxx>]

On Fri, Jul 1, 2022 at 1:10 PM Andy Shevchenko
<andy.shevchenko@xxxxxxxxx> wrote:
>
> On Fri, Jul 1, 2022 at 1:06 PM Bartosz Golaszewski <brgl@xxxxxxxx> wrote:
> >
> > All polling system calls have some way of being instructed to block
> > indefinitely until some event is registered on the file descriptor.
> >
> > Make both the gpiod_chip_wait_info_event() and
> > gpiod_line_request_wait_edge_event() accept negative timeout values in
> > which case the underlying ppoll() will block indefinitely.
>
> Long time no user space done by me, so here my silly question: how to
> kill a task that is blocking indefinitely in ppoll()?
>

Send a signal to it. It will return -1 and set errno to EINTR. Unless
you explicitly masked all signals. In that case kill -9 still works.
:)

Bart