[Xcb] [handoff v3 regression] gtkperf freezes xcb_wait_for_reply()/_XReply()

Jamey Sharp jamey at minilop.net
Mon Nov 3 08:19:44 PST 2008

On Sun, Nov 02, 2008 at 11:57:09AM +0100, Maarten Maathuis wrote:
> When running the "GtkDrawingArea - Text" of gtkperf it'll freeze
> almost certainly with the handoff patches applied, removing these
> solved the issue. I got the following backtrace when interrupting it.
> #0  0x00007fc6f74826e3 in __select_nocancel () from /lib/libc.so.6
> #1  0x00007fc6f491d9c4 in _xcb_conn_wait () from /usr/lib/libxcb.so.1
> #2  0x00007fc6f491f327 in xcb_wait_for_reply () from /usr/lib/libxcb.so.1
> #3  0x00007fc6f6f008c8 in _XReply () from /usr/lib/libX11.so.6
> #4  0x00007fc6f6efb38f in _XSeqSyncFunction () from /usr/lib/libX11.so.6

This type of hang, in _XSeqSyncFunction, is the symptom of a bug I
noticed a few weeks ago. Last week Keith Packard tracked it down and
provided a patch, and Josh and I produced a minimal test case and
cleaned up Keith's patch.

The test case and Xlib patch are attached. See the explanation there.

Josh and I wanted to put out an XCB 1.1.92 release with handoff applied
last week but ran out of time after fixing the wiki. If somebody were to
release XCB 1.2-RC2 (1.1.92) that'd be awesome. We merged and cleaned up
the duplicate release instructions on the wiki, so just follow those.

By the way, this was a bug in Xlib before any XCB stuff was merged in,
but it was almost impossible to trigger before Xlib/XCB with handoff.

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