On 6/16/21 5:36 AM, Neel Chauhan wrote:
Hi current@,
First off, sorry if I spammed developers@ and other mailing lists with
my previous message, and to bz@/hselasky@/manu@ sent so many duplicate
emails.
Right now, I am attempting to update the drm-kmod driver to the Linux
5.7 code, and am having an issue with the pmap lock. I am new-ish to the
kernel, meaning not a whole lot of "experience", but do have patches in
src.
But like it not we need kernel newbies, they're the next generation of
experts. If we don't, we'd be the next Minix with **zero** development
since Tanenbaum retired.
Going back, the code in question is here:
https://github.com/neelchauhan/drm-kmod/blob/5.7-wip/drivers/gpu/drm/i915/gem/i915_gem_mman.c#L346
The lines important are 346-356, but lines of interest are also the
non-"#ifdef __linux__" sections of vm_fault_cpu().
The code gives this error: panic: Assertion
vm_object_busied((m->object)) failed at /usr/src/sys/vm/vm_page.c:5455
I have attached the core dump log.
To those who aren't graphics driver experts, it happens when I load Xorg
when Xorg attempts to map the I/O to userspace. But I feel this is more
of me not using page locks correctly (which is needed for the pmap), or
maybe a linuxkpi issue, rather than a graphics-specific issue.
I spent days on this (all my non-$DAYJOB hours at one point + all my
weekends) and haven't figured out the locks completely. Does anyone have
suggestions to what I'm doing wrong in my code and locks?
If it is important, OpenBSD's version of this code is here:
https://github.com/openbsd/src/blob/2207c4325726fdc5c4bcd0011af0fdf7d3dab137/sys/dev/pci/drm/i915/gem/i915_gem_mman.c#L459
(lines 459-523, but some calls are unsurprisingly different).
Hope you all can help.
Hi,
Do you have the full backtrace?
Doesn't this code work in the current DRM - kmod? What changed? Did you
perhaps miss a patch?
--HPS
