Bug 94461 - Compiz freezes when undocking Lenovo T450s, hang in xcb_wait_for_reply/wait_for_reply/_xcb_conn_wait
Summary: Compiz freezes when undocking Lenovo T450s, hang in xcb_wait_for_reply/wait_f...
Status: RESOLVED DUPLICATE of bug 108960
Alias: None
Product: XCB
Classification: Unclassified
Component: Library (show other bugs)
Version: 1.11
Hardware: x86-64 (AMD64) Linux (All)
: medium major
Assignee: xcb mailing list dummy
QA Contact: xcb mailing list dummy
URL:
Whiteboard:
Keywords:
Depends on:
Blocks:
 
Reported: 2016-03-09 14:27 UTC by cs_gon
Modified: 2019-02-16 12:44 UTC (History)
0 users

See Also:
i915 platform:
i915 features:

Attachments
compiz stack trace (10.00 KB, text/plain)
2016-03-09 14:27 UTC, cs_gon 		Details
compiz screen shot (374.98 KB, image/jpeg)
2016-03-09 14:31 UTC, cs_gon 		Details
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Description cs_gon 2016-03-09 14:27:09 UTC 
Created attachment 122174 [details]
compiz stack trace

When undocking my Lenovo T450s from the docking station (with external monitor connected), compiz frequently freezes, especially when an application is running, that does a lot of screen updates (i.e. terminal with top running at a low refresh frequency, or something like glxgears).

This happens since updating a 14.04 system to the Wily HWE stack (libxcb 1.10), but it is also reproducible when using Xenial (with libxcb 1.11).

When compiz freezes, the screen gets kinda corrupted (will attach an screen shot). The screen does not get updated, only the mouse cursor works. When docking the notebook again, compiz recovers most of the time. Sometimes though, nothing happens and compiz keeps frozen. In this state only a restart of compiz or the X-Server (from the text console) help to get the system usable again.

When doing a stack trace on compiz, it hangs in xcb_wait_for_reply / wait_for_reply / _xcb_conn_wait. I will attach the full stack trace. The stack trace was captured with libxcb 1.10, but as mentioned above, the problem does also happen with libxcb 1.11).
Comment 1 cs_gon 2016-03-09 14:31:02 UTC 
Created attachment 122175 [details]
compiz screen shot

Here the screen shot of the hanging compiz.
Comment 2 cs_gon 2016-03-09 16:42:01 UTC 
Some additional information:

I'm not sure if this is a libxcb bug, but I found some older bugs with pretty much the same symptoms and call traces. This is the reason I reported it here. If this is not a libxcb bug, hopefully you can point me in the right direction.

The problem started to appear after updating to the Wily HWE stack (with kernel 4.2). I cannot reproduce the problem with older kernels (e.g. 3.16 or 3.18), but with any newer kernel, up to the latest 4.5 versions (including drm-next and drm-intel-nightly branches).

As far I can see, compiz only uses one thread to do X calls. Especially for the stack trace I attached, no other compiz threads were in any X calls. 

Compiz does not call XInitThreads(), but I added the call before any other X calls, just in case. But then compiz does not fully start (shows the Unity panels, but does not draw a background), and then hangs in a XLockDisplay() call. And just like before, the other threads are not in any X calls. So IMHO that does seem point in the direction of libxcb!?

If you need any more information, please let me know. Thanks!
Comment 3 Daniel Stone 2019-02-16 12:44:03 UTC 

*** This bug has been marked as a duplicate of bug 108960 ***

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