Hi. (This is not really a bugreport, just a notice to inform potential victims. :) AFAICT it's not DragonFly specific issue, see below.)
I'm experiencing occasional freezes running DragonFly desktop on a Baytrail system (namely Intel Celeron J1900) with machdep.mwait.CX.idle set to AUTODEEP (which enables C6 and C7 on this system). Limiting it to C1/1 makes the system stable. Interestingly, the problem is evolving somewhat... The system was stable before commit 2c9916c+ (drm/i915: Upgrade to Linux 4.0). After this update I started to experience the hangs, approximately once a day. I didn't know about the "C1 workaround" at that time, so I just locally reverted that commit to get the stable system. Commit 477eb7f+ (drm/i915: Update to Linux 4.1) somehow fixed it, and system was stable again, even with machdep.mwait.CX.idle=AUTODEEP. But commit 19c468b+ (drm/i915: Update to Linux 4.2) brought the hangs back, and this time I've "resolved" it via machdep.mwait.CX.idle=C1/1. According to these bugreports from linux users... https://bugs.freedesktop.org/show_bug.cgi?id=88012 https://bugzilla.kernel.org/show_bug.cgi?id=109051 ... it doesn't seem to be DragonFly specific issue but more probably a bug in shared i915 code. Those discussions also confirm that bug was introduced somewhere after linux 3.16, then disappeared for a while during 4.1 and was brought back with 4.2 (and remains to 4.5). So far, nobody has come with a solution, but everyone confirm that "C1 workaround" prevents from hangs. HTH. -- Dan
