Bug 109218 - PresentPixmap doesn't work with XSync fences, crashes server
Summary: PresentPixmap doesn't work with XSync fences, crashes server
Status: NEW
Alias: None
Product: xorg
Classification: Unclassified
Component: Driver/intel (show other bugs)
Version: unspecified
Hardware: x86-64 (AMD64) Linux (All)
: medium major
Assignee: Chris Wilson
QA Contact: Intel GFX Bugs mailing list
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Reported: 2019-01-03 23:09 UTC by Yuxuan Shui
Modified: 2019-01-08 21:55 UTC (History)
0 users

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Description Yuxuan Shui 2019-01-03 23:09:06 UTC
In an experimental branch of compton, I tried using PresentPixmap with xrender to achieve tear free display. I discovered that the XSync fence passed to PresentPixmap never gets triggered, and when I kill compton, the whole server crashes.

I don't have a stack trace, but X server crashed in a function called AttendClient trying to dereference 0x28.

Maybe intel driver only supports fences created via DRI3FenceFromFD. That should've been made clear somewhere (where?), and X server definitely shouldn't crash.
Comment 1 Yuxuan Shui 2019-01-03 23:09:49 UTC
BTW, I suspected the fence because when I don't pass a fence to PresentPixmap, everything seems to work fine.
Comment 2 Yuxuan Shui 2019-01-08 21:55:24 UTC
If you want a testcase, you can try commit 055364431a0706b97c2875d5501dc20dbcf1bdeb of compton.


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