Created attachment 114043 [details]
dmesg linux_4rc2

cape verde 
kernel 4rc2/3.19 x86 
llvm svn230872
radeon git
xorg 1.17.1
mesa git

git bisect... gives this:

5f1cef76f9bbaae772120dcb38e0b98d68a93f26 is the first bad commit
commit 5f1cef76f9bbaae772120dcb38e0b98d68a93f26
Author: Marek Olšák <marek.olsak@amd.com>
Date:   Sat Feb 7 13:19:38 2015 +0100

    r600g,radeonsi: use fences to implement PIPE_QUERY_GPU_FINISHED

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89014

    Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>

:040000 040000 aae0244556c43c9d03243992143a8c9fc0128977
7f320431b51c3f55f243448b0b5dc3031feb6abb M    src


64bit system is affected too but GPU was hung after about one hour.