wl_buffer is not released for long time.

Pekka Paalanen ppaalanen at gmail.com
Thu Mar 15 08:40:59 UTC 2018

On Thu, 15 Mar 2018 00:19:10 +0000
Sichem Zhou <sichem.zh at gmail.com> wrote:

> Dear Pekka,
> Thanks for your idea on this, I inserted a callback in the `surface_commit`
> function in libweston. From the log I can see that the `surface commit` was
> blocked on the server side until some other events happen. On the client
> side it was clear that I committed two buffers then sleeped because of
> lacking available buffers. I am using libweston and currently I didn't
> setup any input callbacks. All I did was setting up an interface to set
> views in background layers then call `wl_display_run()`. I hope to know is
> there anyways to follow wayland server event queues in libweston?


there is only one event queue in the server-side per client. IIRC, it's
not really even a queue as much as just a buffer.

You can use WAYLAND_DEBUG=server environment variable to have
libwayland-server print all protocol messages at the time they are
processed. That means, the time when requests are being dispatched, and
events are being queued for sending. There is WAYLAND_DEBUG=client
working the same way for clients, but it might be confusing if it is
set for multiple clients at the same time.

If you need to check the messages on "the wire" instead, the Wayland
website extras have a list of some debugger programs. Messages enter
the wire on flush after send. Forgetting to flush will show the message
in WAYLAND_DEBUG=1 output, but it might not be actually sent at the

This issue could also be a client bug. If you do not ensure that all
requests have been flushed out before going to sleep in poll(), they
might never actually reach the server until something else happens.

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