[Xcb] Display freeze hanging in xcb_wait_for_reply

Uli Schlachter psychon at znc.in
Thu Sep 25 03:29:11 PDT 2014


Am 25.09.2014 um 12:21 schrieb Daniel Kuhne:
> We are facing display freeze with libxcb-1.9 in multithreaded environment.
> We see this freeze when we set resolution of our application to display
> resolution,
> graphic drivers performs a flip instead of a blit operation. In that case,
> after some frames,
> we will never come back from xcb_wait_for_reply() in XReply() inside
> xcb_io.c. If
> we set resolution not to fullscreen, we do get a blit for each frame, we
> never fall into
> a display freeze. We are wondering if this a known issue with xcb?

Nope, no known issue with xcb and it's unlikely to be an xcb issue at all. As
far as I know, this could either be an issue with Xlib and threads[0] or with
mesa, DRI3 and some graphics driver where an event that mesa waits for is never
generated (although it should hang in xcb_wait_for_special_event() in this case,
thus the former is more likely).

> Could you please say how we should provide more information. Where should
> we do some
> debug prints?

How about a backtrace?


If you have to type the letters "A-E-S" into your source code, you're doing it

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