kern/60703: panic: LOCKDEBUG: Mutex error: kmem_intr_free,397: allocation contains active lock

["Manuel.Bouyer%lip6.fr@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60703
>Category:       kern
>Synopsis:       panic: LOCKDEBUG: Mutex error: kmem_intr_free,397: allocation contains active lock
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Sep 09 13:25:00 +0000 2026
>Originator:     Manuel Bouyer
>Release:        NetBSD 11.0_STABLE
>Organization:
>Environment:
System: NetBSD armandeche.soc.lip6.fr 11.0_STABLE NetBSD 11.0_STABLE (GENERIC_CAN) #1: Thu Sep 3 12:51:47 CEST 2026 bouyer%armandeche.soc.lip6.fr@localhost:/local/armandeche1/tmp/build/amd64/obj/local/armandeche2/netbsd-11/src/sys/arch/amd64/compile/GENERIC_CAN amd64
Architecture: x86_64
Machine: amd64
>Description:
	This is a desktop workstation. At the time of the panic I had one
	application running, reading data from a USB device and printing
	line of text in its xterm, in a tight loop (top did show high CPU 
	usage for X, xterm, system and interrupts.
	At some point the system paniced, crash on the core dump shows:
armandeche# crash -M netbsd.3.core -N netbsd.3
Crash version 11.0_STABLE, image version 11.0_STABLE.
System panicked: LOCKDEBUG: Mutex error: kmem_intr_free,397: allocation contains active lock
Backtrace from time of crash is available.
crash> tr
usb_findvendor_real() at 0
kern_reboot() at kern_reboot+0x93
vpanic() at vpanic+0x17b
panic() at printf_nostamp
lockdebug_abort1() at lockdebug_more.part.0
kmem_intr_free() at kmem_intr_free+0xb4
gen8_ppgtt_create() at gen8_ppgtt_create+0x277
i915_ppgtt_create() at i915_ppgtt_create+0x2b
i915_gem_create_context() at i915_gem_create_context+0x34f
i915_gem_context_open() at i915_gem_context_open+0x5d
i915_gem_open() at i915_gem_open+0x9e
drm_file_alloc() at drm_file_alloc+0x16c
drm_open() at drm_open+0x157
cdev_open() at cdev_open+0x135
spec_open() at spec_open+0x23d
VOP_OPEN() at VOP_OPEN+0x3e
vn_open() at vn_open+0x33c
do_open() at do_open+0xb3
do_sys_openat() at do_sys_openat+0x72
sys_open() at sys_open+0x24
syscall() at syscall+0x9d
--- syscall (number 5) ---
syscall+0x9d:

The CPU with integrated graphic is:
cpu0: highest basic info 00000016
cpu0: highest extended info 80000008
cpu0: "Intel(R) Core(TM) i5-8400 CPU @ 2.80GHz"
cpu0: Intel 7th or 8th gen Core (Kaby Lake, Coffee Lake) or Xeon E (Coffee Lake) (686-class), 2808.00 MHz
cpu0: CPU base freq 2800000000 Hz
cpu0: CPU max freq 4000000000 Hz
cpu0: TSC freq CPUID 2808000000 Hz
cpu0: family 0x6 model 0x9e stepping 0xa (id 0x906ea)

fgrep drm /var/run/dmesg.boot:
i915drmkms0 at pci0 dev 2 function 0: Intel UHD Graphics 630 (rev. 0x00)
[drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[drm] Driver supports precise vblank timestamp query.
i915drmkms0: interrupting at msi5 vec 0 (i915drmkms0)
i915drmkms0: notice: Failed to load DMC firmware i915/kbl_dmc_ver1_04.bin. Disabling runtime power management.
[drm] failed to retrieve link info, disabling eDP
[drm] Initialized i915 1.6.0 20200114 for i915drmkms0 on minor 0
intelfb0 at i915drmkms0
[drm] DRM_I915_DEBUG enabled
[drm] DRM_I915_DEBUG_GEM enabled


>How-To-Repeat:
	occured only once at this time
>Fix: