drm2, i915kms cause instant lock-up

Mon Feb 20 23:52:25 UTC 2017

With a kernel and world from r313943 sources (circa
Feb 19, 2017), kldload of either drm2.ko or i915kms.ko
will lock up the system.  There is no keyboard response,
screen output, or panic.  Just a locked up system.

A kernel from r313027 and its modules boots fine.
'kldload drm2.ko' yields the following in /var/log/messages:

agp0: <Intel GM965 SVGA controller> on vgapci0
agp0: aperture size is 256M, detected 7676k stolen memory
info: [drm] Initialized drm 1.1.0 20060810

'kldload drm2.ko' yields the following in /var/log/messages:
drmn0: <Intel i965GM> on vgapci0
intel_iicbb0 on drmn0
iicbus0: <Philips I2C bus> on iicbb0 addr 0xf2
iic0: <I2C generic I/O> on iicbus0
iicbus1: <Philips I2C bus> on intel_gmbus0
iic1: <I2C generic I/O> on iicbus1
intel_iicbb1 on drmn0
iicbus2: <Philips I2C bus> on iicbb1 addr 0xf2
iic2: <I2C generic I/O> on iicbus2
iicbus3: <Philips I2C bus> on intel_gmbus1
iic3: <I2C generic I/O> on iicbus3
intel_iicbb2 on drmn0
iicbus4: <Philips I2C bus> on iicbb2 addr 0xf2
iic4: <I2C generic I/O> on iicbus4
iicbus5: <Philips I2C bus> on intel_gmbus2
iic5: <I2C generic I/O> on iicbus5
intel_iicbb3 on drmn0
iicbus6: <Philips I2C bus> on iicbb3 addr 0xf2
iic6: <I2C generic I/O> on iicbus6
iicbus7: <Philips I2C bus> on intel_gmbus3
iic7: <I2C generic I/O> on iicbus7
intel_iicbb4 on drmn0
iicbus8: <Philips I2C bus> on iicbb4 addr 0xf2
iic8: <I2C generic I/O> on iicbus8
iicbus9: <Philips I2C bus> on intel_gmbus4
iic9: <I2C generic I/O> on iicbus9
intel_iicbb5 on drmn0
iicbus10: <Philips I2C bus> on iicbb5 addr 0xf2
iic10: <I2C generic I/O> on iicbus10
iicbus11: <Philips I2C bus> on intel_gmbus5
iic11: <I2C generic I/O> on iicbus11
info: [drm] MSI enabled 1 message(s)
info: [drm] Supports vblank timestamp caching Rev 1 (10.10.2010).
info: [drm] Driver supports precise vblank timestamp query.
composite sync not supported
intel_sdvo_ddc_proxy397632 on drmn0
intel_sdvo_ddc_proxy397632: detached
intel_sdvo_ddc_proxy397664 on drmn0
intel_sdvo_ddc_proxy397664: detached
drmn0: taking over the fictitious range 0xe0000000-0xf0000000
info: [drm] initialized overlay support
info: [drm] Connector LVDS-1: get mode from tunables:
info: [drm]   - kern.vt.fb.modes.LVDS-1
info: [drm]   - kern.vt.fb.default_mode
info: [drm] Connector VGA-1: get mode from tunables:
info: [drm]   - kern.vt.fb.modes.VGA-1
info: [drm]   - kern.vt.fb.default_mode
info: [drm] Connector SVIDEO-1: get mode from tunables:
info: [drm]   - kern.vt.fb.modes.SVIDEO-1
info: [drm]   - kern.vt.fb.default_mode
composite sync not supported
fbd0 on drmn0
VT: Replacing driver "vga" with new "fb".
info: [drm] Initialized i915 1.6.0 20080730 for drmn0 on minor 0
 
A diff of dmesg.boot for the good kernel and bad kernel shows

--- /root/dmesg.good	2017-02-20 13:30:06.707702000 -0800
+++ /root/dmesg.bad	2017-02-20 13:42:10.271942000 -0800
@@ -2,11 +2,11 @@
 Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
 	The Regents of the University of California. All rights reserved.
 FreeBSD is a registered trademark of The FreeBSD Foundation.
-FreeBSD 12.0-CURRENT #3 r313027: Mon Feb 20 11:59:15 PST 2017
+FreeBSD 12.0-CURRENT #1 r313943: Sun Feb 19 09:18:03 PST 2017
     root at laptop-kargl:/mnt/obj/mnt/src/sys/MOBILE i386
 FreeBSD clang version 3.9.1 (tags/RELEASE_391/final 289601) (based on LLVM 3.9.1)
 VT(vga): text 80x25
-CPU: Intel(R) Core(TM)2 Duo CPU     T7250  @ 2.00GHz (1995.05-MHz 686-class CPU)
+CPU: Intel(R) Core(TM)2 Duo CPU     T7250  @ 2.00GHz (1995.04-MHz 686-class CPU)
   Origin="GenuineIntel"  Id=0x6fd  Family=0x6  Model=0xf  Stepping=13
   Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
   Features2=0xe3bd<SSE3,DTES64,MON,DS_CPL,VMX,EST,TM2,SSSE3,CX16,xTPR,PDCM>
@@ -15,7 +15,7 @@
   VT-x: (disabled in BIOS) HLT,PAUSE
   TSC: P-state invariant, performance statistics
 real memory  = 4294967296 (4096 MB)
-avail memory = 3663994880 (3494 MB)
+avail memory = 3665018880 (3495 MB)
 Event timer "LAPIC" quality 100
 ACPI APIC Table: <DELL   M08    >
 FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
@@ -24,7 +24,7 @@
 ioapic0 <Version 2.0> irqs 0-23 on motherboard
 random: entropy device external interface
 kbd1 at kbdmux0
-module_register_init: MOD_LOAD (vesa, 0xc0bf7440, 0) error 19
+module_register_init: MOD_LOAD (vesa, 0xc0ae6db0, 0) error 19
 nexus0
 vtvga0: <VT VGA driver> on motherboard
 acpi0: <DELL M08    > on motherboard
@@ -42,7 +42,7 @@
 attimer0: <AT timer> port 0x40-0x43,0x50-0x53 irq 2 on acpi0
 Timecounter "i8254" frequency 1193182 Hz quality 0
 Event timer "i8254" frequency 1193182 Hz quality 100
-Timecounter "ACPI-safe" frequency 3579545 Hz quality 850
+Timecounter "ACPI-fast" frequency 3579545 Hz quality 900
 acpi_timer0: <24-bit timer at 3.579545MHz> port 0x1008-0x100b on acpi0
 pcib0: <ACPI Host-PCI bridge> on acpi0
 pcib0: failed to parse resources: AE_AML_NO_RESOURCE_END_TAG

The module_register_init difference seems suspicious.

-- 
Steve
20161221 https://www.youtube.com/watch?v=IbCHE-hONow
