drm_poll / poll_wait kernel panic on Wayland compositors

[valpackett]

This FreeBSD commit: freebsd/freebsd-src@24eb9f4

results in panic: selrecord: No free selfd on selq (selrecord - linux_poll_wait - drm_poll) when starting a Wayland compositor (e.g. sway).

Reverting that commit fixes the problem! But that's not a real fix…

[hselasky]

Should be fixed by:
https://svnweb.freebsd.org/changeset/base/324597

[valpackett]

Yeah, updated my system, it works! Thanks @hselasky.

[valpackett]

By the way, I've been getting this linux_dev_mmap_single panic sometimes. One time when launching an SDL2 app on Wayland, one time when launching an Xorg app on XWayland (which doesn't work for now anyway…)

[hselasky]

Can you do:
gdb
file /boot/kernel/linuxkpi.ko
info line *(void *)(linux_dev_mmap_single+0x32e)

[hselasky]

Looks like a NULL pointer.

[valpackett]

Line 1334 of "/usr/src/sys/compat/linuxkpi/common/src/linux_compat.c" starts at address 0x1f3e <linux_dev_mmap_single+814>
   and ends at 0x1f5b <linux_dev_mmap_single+843>.

		if (vmap->vm_ops->fault == NULL) {
			*object = cdev_pager_allocate(vm_private_data, OBJT_DEVICE,
			    &linux_cdev_pager_ops[1], size, nprot, *offset,
			    curthread->td_ucred);

[hselasky]

Yepp, that's it. Can you try this patch.
linuxkpi.diff.txt

[valpackett]

Thanks! Played three SDL2 games under a Wayland compositor, did not see panics.

[hselasky]

Here is the final fix:
https://svnweb.freebsd.org/changeset/base/325767

Thank you for testing!