2015-01-28 17:25 GMT+02:00 Derek Foreman <[email protected]>:
> To fix a shutdown crash in weston's x11 compositor I want to move the
> weston X window close to an idle handler.
>
> Since idle handlers are processed at the start of an event loop, the
> handler that deals with window close will run at the start of the
> next input_loop dispatch, after which the dispatcher blocks on epoll
> forever (since all input events that will ever occur have been consumed).
>
> Dispatching idle callbacks both at the start and end of event-loop
> processing will prevent this permanent blocking.
>
> Note that just moving the callback dispatch could theoretically
> result in an idle callback being delayed indefinitely while waiting
> for epoll_wait() to complete.
>
> Callbacks are removed from the list when they're run, so the second
> dispatch won't result in any extra calls.
>
> Signed-off-by: Derek Foreman <[email protected]>
> ---
>
> Amusingly, the problem Bill points out is exactly the problem this patch is
> trying to correct.
>
> This version of the patch leaves the original dispatch and adds a second.
>
>
> src/event-loop.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/src/event-loop.c b/src/event-loop.c
> index 1f571ba..d257d78 100644
> --- a/src/event-loop.c
> +++ b/src/event-loop.c
> @@ -421,10 +421,12 @@ wl_event_loop_dispatch(struct wl_event_loop *loop, int
> timeout)
>
> wl_event_loop_process_destroy_list(loop);
>
> + wl_event_loop_dispatch_idle(loop);
> +
How does this fix the problem? The idle callbacks are still called
before the epoll_wait(), so shouldn't the problem you describe in the
commit message still happen?
Besides, the idle callbacks are anyway going to be called very soon at
the next loop in wl_display_run() after wl_event_loop_dispatch()
returns. Or is the post_dispatch_check() call below involved somehow?
--
Giulio
> do {
> n = post_dispatch_check(loop);
> } while (n > 0);
> -
> +
> return 0;
> }
>
> --
> 2.1.4
>
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