kern/49252: drm2 panic

[apb%cequrux.com@localhost]

>Number:         49252
>Category:       kern
>Synopsis:       drm2 panic
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Oct 02 10:50:00 +0000 2014
>Originator:     Alan Barrett
>Release:        NetBSD 7.99.1
>Organization:
Not much
>Environment:
NetBSD 7.99.1 i386
Sources checked out from CVS with -D '2014-09-26 00:00 UTC'.
>Description:
	Yet another drm2 panic.
	The panic message is "cpu_switchto: switching above IPL_SCHED (8)"

	The backtrace from gdb is:

#10 0xc08b9f40 in vpanic (
    fmt=fmt@entry=0xc01003d1 <cpu_switchto+33> "cpu_switchto: switching above IPL_SCHED (%d)", ap=ap@entry=0xdea26cc0 "\b")
    at src/sys/kern/subr_prf.c:338
#11 0xc08b9fda in panic (
    fmt=0xc01003d1 <cpu_switchto+33> "cpu_switchto: switching above IPL_SCHED (%d)") at src/sys/kern/subr_prf.c:256
#12 0xc01003ce in cpu_switchto ()
#13 0xc4ea8040 in ?? ()
#14 0xc0659c24 in sleepq_block (timo=timo@entry=0, catch_p=catch_p@entry=true)
    at src/sys/kern/kern_sleepq.c:264
#15 0xc062a53a in cv_wait_sig (cv=cv@entry=0xc49ad634,
    mtx=mtx@entry=0xc49ad7c8)
    at src/sys/kern/kern_condvar.c:239
#16 0xc03a6e3c in __wait_seqno (ring=ring@entry=0xc49ad574,
    seqno=seqno@entry=2169, reset_counter=reset_counter@entry=0,
    interruptible=interruptible@entry=true, timeout=timeout@entry=0x0,
    file_priv=file_priv@entry=0xc6641cdc)
    at src/sys/external/bsd/drm2/dist/drm/i915/i915_gem.c:1429
#17 0xc03a8dd5 in i915_gem_object_wait_rendering__nonblocking (
    obj=obj@entry=0xc4f27200, file_priv=0xc6641cdc, readonly=<optimized out>)
    at src/sys/external/bsd/drm2/dist/drm/i915/i915_gem.c:1651
#18 0xc03ad3a9 in i915_gem_set_domain_ioctl (dev=0xc4ece64c, data=0xdea26eb0,
    file=0xc6641378)
    at src/sys/external/bsd/drm2/dist/drm/i915/i915_gem.c:1702
#19 0xc02bfb9c in drm_ioctl (fp=0xc77e6e00, cmd=2148295775, data=0xdea26eb0)
    at src/sys/external/bsd/drm2/drm/drm_drv.c:664
#20 0xc08d1080 in sys_ioctl (l=0xc7758aa0, uap=0xdea26f68, retval=0xdea26f60)
    at src/sys/kern/sys_generic.c:681
#21 0xc08dc743 in sy_call (rval=0xdea26f60, uap=0xdea26f68, l=0xc7758aa0,
    sy=<optimized out>) at src/sys/sys/syscallvar.h:61
#22 sy_invoke (code=54, rval=0xdea26f60, uap=0xdea26f68, l=0xc7758aa0,
    sy=<optimized out>) at src/sys/sys/syscallvar.h:85
#23 syscall (frame=0xdea26fa8)
    at src/sys/arch/x86/x86/syscall.c:156
#24 0xc01005c6 in Xsyscall ()
#25 0xdea26fa8 in ?? ()
Backtrace stopped: previous frame inner to this frame (corrupt stack?)
(gdb) p panicstr
$1 = 0xc104f880 <scratchstr> "cpu_switchto: switching above IPL_SCHED (8)"
	
>How-To-Repeat:
	Nothing special.  Just trying to use my laptop with a drm2 kernel.
	DRM-related panics usually occur when I am moving or clicking the
	mouse while X11 is active.

$ egrep -i 'vga|drm|kms' /var/run/dmesg.boot
acpivga0 at acpi0 (GFX0): ACPI Display Adapter
acpiout0 at acpivga0 (DD01, 0x0100): ACPI Display Output Device
acpiout1 at acpivga0 (DD02, 0x0400): ACPI Display Output Device
acpiout2 at acpivga0 (DD03, 0x0300): ACPI Display Output Device
acpiout3 at acpivga0 (DD04, 0x0301): ACPI Display Output Device
acpiout4 at acpivga0 (DD05, 0x0302): ACPI Display Output Device
acpiout5 at acpivga0 (DD06, 0x0303): ACPI Display Output Device
acpiout6 at acpivga0 (DD07, 0x0304): ACPI Display Output Device
acpiout7 at acpivga0 (DD08, 0x0305): ACPI Display Output Device
acpivga0: ERROR: unknown output device acpiout0
acpivga0: ERROR: unknown output device acpiout2
acpivga0: ERROR: unknown output device acpiout3
acpivga0: ERROR: unknown output device acpiout4
acpivga0: ERROR: unknown output device acpiout5
acpivga0: ERROR: unknown output device acpiout6
acpivga0: ERROR: unknown output device acpiout7
acpivga0: connected output devices:
acpivga0:   0x0400 (acpiout1): Unknown Output Device, head 0
vendor 10de product 1054 (VGA display, revision 0xa1) at pci1 dev 0 function 0 not configured
i915drmkms0 at pci0 dev 2 function 0: vendor 8086 product 0116 (rev. 0x09)
drm: Memory usable by graphics device = 2048M
drm: Supports vblank timestamp caching Rev 2 (21.10.2013).
drm: Driver supports precise vblank timestamp query.
i915drmkms0: interrupting at ioapic0 pin 16 (i915)
drm: Wrong MCH_SSKPD value: 0x16040307
drm: This can cause pipe underruns and display issues.
drm: Please upgrade your BIOS to fix this.
intelfb0 at i915drmkms0
i915drmkms0: info: registered panic notifier
drm: Enabling RC6 states: RC6 on, RC6p off, RC6pp off

>Fix:
	Unknown