Created attachment 116344 [details] output from dmesg | tail See attached log. Note the /sys/class/drm/card0/error file is zero size, so not helpful.
"Note the /sys/class/drm/card0/error file is zero size, so not helpful." No, ls lies. Just cat it: $ cat sys/class/drm/card0/error | bz2 > error.bz2
It is not possible to debug the issue without the GPU crash dump. Please reopen if you are able to attach the contents of /sys/class/drm/card0/error after the GPU hang and before a reboot.
This bug is intertwined with 90890, and I just reported there that my problem with the Dell SX280 may be fixed with kernel 4.0.6-300.fc22 and xorg-x11-drv-intel-2.99.917-12.20150615.fc22 or at least I have run unusually long without having the problem show up today.
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