Re: Kernel crash during video transcoding

I'm recompiling the kernel using GENERIC at the moment but I'm not sure how
to enable debugging in i915 kms, there is no compile option for that, am I
missing something ?

Le lun. 10 août 2020 à 08:44, Hans Petter Selasky <hps_at_selasky.org> a
écrit :

> Hi,
>
> On 2020-08-10 00:19, Alexandre Levy wrote:
> > Hi,
> >
> > I installed the port drm-devel-kmod for Plex to be able to transcode
> videos
> > using the integrated GPU of my Intel Celeron G5900.
> >
> > I'm running r364031 and the kernel is compiled with GENERIC-NODEBUG
> profile.
> >
> > Transcoding has been working fine for quite a while now but one video
> > transcoding is causing a kernel panic that is reproducible all the time
> > with that particular video. It seems like it's caused by the i915kms
> module
> > (call of i915_gms_fault() in the stack) :
>
> If you compile the kernel using GENERIC and then enable debugging in the
> i915 kms and reproduce, we might get a more clear picture!
>
> It is a so called NULL pointer you've experienced.
>
> --HPS
>
> >
> > Fatal trap 12: page fault while in kernel mode
> > cpuid = 0; apic id = 00
> > fault virtual address   = 0xdf
> > fault code              = supervisor read data, page not present
> > instruction pointer     = 0x20:0xffffffff80bdd2b4
> > stack pointer           = 0x0:0xfffffe00d2be56d0
> > frame pointer           = 0x0:0xfffffe00d2be56d0
> > code segment            = base 0x0, limit 0xfffff, type 0x1b
> >                          = DPL 0, pres 1, long 1, def32 0, gran 1
> > processor eflags        = interrupt enabled, resume, IOPL = 0
> > current process         = 4611 (Plex Transcoder)
> > trap number             = 12
> > panic: page fault
> > cpuid = 0
> > time = 1596976796
> > KDB: stack backtrace:
> > db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame
> > 0xfffffe00d2be5390
> > vpanic() at vpanic+0x182/frame 0xfffffe00d2be53e0
> > panic() at panic+0x43/frame 0xfffffe00d2be5440
> > trap_fatal() at trap_fatal+0x387/frame 0xfffffe00d2be54a0
> > trap_pfault() at trap_pfault+0x4f/frame 0xfffffe00d2be54f0
> > trap() at trap+0x271/frame 0xfffffe00d2be5600
> > calltrap() at calltrap+0x8/frame 0xfffffe00d2be5600
> > --- trap 0xc, rip = 0xffffffff80bdd2b4, rsp = 0xfffffe00d2be56d0, rbp =
> > 0xfffffe00d2be56d0 ---
> > _rw_wowned() at _rw_wowned+0x4/frame 0xfffffe00d2be56d0
> > vm_page_busy_acquire() at vm_page_busy_acquire+0x141/frame
> > 0xfffffe00d2be5710
> > remap_io_mapping() at remap_io_mapping+0x120/frame 0xfffffe00d2be5760
> > i915_gem_fault() at i915_gem_fault+0x25f/frame 0xfffffe00d2be57d0
> > linux_cdev_pager_populate() at linux_cdev_pager_populate+0x11b/frame
> > 0xfffffe00d2be5840
> > vm_fault() at vm_fault+0x3d1/frame 0xfffffe00d2be5950
> > vm_fault_trap() at vm_fault_trap+0x60/frame 0xfffffe00d2be5990
> > trap_pfault() at trap_pfault+0x19c/frame 0xfffffe00d2be59e0
> > trap() at trap+0x3f1/frame 0xfffffe00d2be5af0
> > calltrap() at calltrap+0x8/frame 0xfffffe00d2be5af0
> > --- trap 0xc, rip = 0x80296659a, rsp = 0x7fffffffbd38, rbp = 0x80fc00000
> ---
> > KDB: enter: panic
> >
> > I don't see any crash dump in /var/crash despite having the right
> > configuration and I should have enough space on my swap device (128GB USB
> > drive) :
> >
> > $ cat /etc/rc.conf | grep dump
> > dumpdev="AUTO"
> >
> > $ swapinfo
> > Device          1K-blocks     Used    Avail Capacity
> > /dev/gpt/crash0 121307096        0 121307096     0%
> >
> > $ cat /etc/fstab
> > /dev/gpt/crash0 none    swap    sw              0       0
> >
> > $ dumpon -l
> > gpt/crash0
> >
> > Not sure why no dump was generated, is it because the kernel was compiled
> > with the GENERIC-NODEBUG profile ? However I see various KDB options in
> the
> > GENERIC profile that are inherited by GENERIC-NODEBUG.
> >
> > Happy to recompile the kernel with GENERIC profile if it's required.
> >
> > Thank you.
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>