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Fortunately I was able to resolve this after 2 months of frustration, but I thought I would post the problem and solution for others.
After the update to kernel 4.0 (and at least until 4.0.5) my Intel Core-M Broadwell processor (in a Lenovo Yoga Pro 3) would crash a few seconds after launching of any graphical environment, either Wayland or X. The errors as shown in journalctl point to a kernel crash in the intel graphics module:
Jun 16 17:54:03 chris.zuzax.com kernel: BUG: unable to handle kernel NULL pointer dereference at (null)
Jun 16 17:54:03 chris.zuzax.com kernel: IP: [< (null)>] (null)
Jun 16 17:54:03 chris.zuzax.com kernel: PGD 22d057067 PUD 24572a067 PMD 0
Jun 16 17:54:03 chris.zuzax.com kernel: Oops: 0010 [#1] PREEMPT SMP
Jun 16 17:54:03 chris.zuzax.com kernel: Modules linked in: rfcomm ecb fuse bnep arc4 iwlmvm mac80211 iTCO_wdt iTCO_vendor_support uvcvideo videobu
Jun 16 17:54:03 chris.zuzax.com kernel: snd_hwdep snd_pcm snd_timer drm snd soundcore intel_gtt i2c_algo_bit thermal i2c_designware_platform batt
Jun 16 17:54:03 chris.zuzax.com kernel: CPU: 0 PID: 733 Comm: gnome-shell Tainted: G U O 4.0.5-1-ARCH #1
Jun 16 17:54:03 chris.zuzax.com kernel: Hardware name: LENOVO 80HE/VIUU4, BIOS A6CN50WW 04/29/2015
Jun 16 17:54:03 chris.zuzax.com kernel: task: ffff88009bc9a880 ti: ffff88008e748000 task.ti: ffff88008e748000
Jun 16 17:54:03 chris.zuzax.com kernel: RIP: 0010:[<0000000000000000>] [< (null)>] (null)
Jun 16 17:54:03 chris.zuzax.com kernel: RSP: 0018:ffff88008e74bb60 EFLAGS: 00010246
Jun 16 17:54:03 chris.zuzax.com kernel: RAX: 0000000000000000 RBX: ffff88025428fb80 RCX: ffff8802253ad700
Jun 16 17:54:03 chris.zuzax.com kernel: RDX: 00000000fffff1af RSI: ffff880252c53dd0 RDI: ffff880252c519f0
Jun 16 17:54:03 chris.zuzax.com kernel: RBP: ffff88008e74bba8 R08: ffff88008e74bdf0 R09: ffff88008c504540
Jun 16 17:54:03 chris.zuzax.com kernel: R10: ffff88024dbbce00 R11: 00000000000000c0 R12: ffff880252c519f0
Jun 16 17:54:03 chris.zuzax.com kernel: R13: 00000000fffff1af R14: ffff88025428fb80 R15: ffff880252c53dd0
Jun 16 17:54:03 chris.zuzax.com kernel: FS: 00007f6051a43980(0000) GS:ffff88025ec00000(0000) knlGS:0000000000000000
Jun 16 17:54:03 chris.zuzax.com kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Jun 16 17:54:03 chris.zuzax.com kernel: CR2: 0000000000000000 CR3: 000000022b5ac000 CR4: 00000000003407f0
Jun 16 17:54:03 chris.zuzax.com kernel: Stack:
Jun 16 17:54:03 chris.zuzax.com kernel: ffffffffa055cc27 ffff880252c53dd8 0000000000000028 0000000000000594
Jun 16 17:54:03 chris.zuzax.com kernel: 0000000000000000 ffff880252c519f0 ffff8802253ace00 ffff88025428fb80
Jun 16 17:54:03 chris.zuzax.com kernel: ffff88008c504540 ffff88008e74bc28 ffffffffa0579634 ffff88023dcecd00
Jun 16 17:54:03 chris.zuzax.com kernel: Call Trace:
Jun 16 17:54:03 chris.zuzax.com kernel: [<ffffffffa055cc27>] ? i915_gem_object_sync+0xe7/0x190 [i915]
Jun 16 17:54:03 chris.zuzax.com kernel: [<ffffffffa0579634>] intel_execlists_submission+0x294/0x4c0 [i915]
Jun 16 17:54:03 chris.zuzax.com kernel: [<ffffffffa05539fc>] i915_gem_do_execbuffer.isra.12+0xabc/0x1230 [i915]
Jun 16 17:54:03 chris.zuzax.com kernel: [<ffffffffa055d349>] ? i915_gem_object_set_to_cpu_domain+0xa9/0x1f0 [i915]
Jun 16 17:54:03 chris.zuzax.com kernel: [<ffffffff811ba2ae>] ? __kmalloc+0x2e/0x2a0
Jun 16 17:54:03 chris.zuzax.com kernel: [<ffffffffa0555471>] i915_gem_execbuffer2+0x141/0x2b0 [i915]
Jun 16 17:54:03 chris.zuzax.com kernel: [<ffffffffa042fcab>] drm_ioctl+0x1db/0x640 [drm]
Jun 16 17:54:03 chris.zuzax.com kernel: [<ffffffffa0555330>] ? i915_gem_execbuffer+0x450/0x450 [i915]
Jun 16 17:54:03 chris.zuzax.com kernel: [<ffffffff8122339b>] ? eventfd_ctx_read+0x16b/0x200
Jun 16 17:54:03 chris.zuzax.com kernel: [<ffffffff811ebc36>] do_vfs_ioctl+0x2c6/0x4d0
Jun 16 17:54:03 chris.zuzax.com kernel: [<ffffffff811f6452>] ? __fget+0x72/0xb0
Jun 16 17:54:03 chris.zuzax.com kernel: [<ffffffff811ebec1>] SyS_ioctl+0x81/0xa0
Jun 16 17:54:03 chris.zuzax.com kernel: [<ffffffff8157a589>] system_call_fastpath+0x12/0x17
Jun 16 17:54:03 chris.zuzax.com kernel: Code: Bad RIP value.
Jun 16 17:54:03 chris.zuzax.com kernel: RIP [< (null)>] (null)
After chatting with a person in #intel-gfx on freenode IRC I was told this is a side effect from the enabling of a new command structure for kernel 4 and higher.
To fix you need to add the following to your kernel line in grub|rEFInd|gummiboot:
i915.enable_execlists=0
The developer suggested they will disable this option in future kernels, but I don't have a bug to track this with so it will be trial and error moving forward.
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This type of information belongs on the wiki, not here.
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Would you like to suggest where on the wiki you see this going?
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Add a note at the bottom on the Intel page: that seems the logical place.
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