On Tue, Oct 25, 2022 at 01:04:53PM +0200, Thomas Zimmermann wrote:

Call sysfb_disable() from aperture_remove_conflicting_pci_devices()
before removing PCI devices. Without, simpledrm can still bind to
simple-framebuffer devices after the hardware driver has taken over
the hardware. Both drivers interfere with each other and results are
undefined.

Reported modesetting errors are shown below.

---- snap ----
rcu: INFO: rcu_sched detected expedited stalls on CPUs/tasks: { 13-.... } 7 jiffies s: 165 root: 0x2000/.
rcu: blocking rcu_node structures (internal RCU debug):
Task dump for CPU 13:
task:X               state:R  running task     stack:    0 pid: 4242 ppid:  4228 flags:0x00000008
Call Trace:
 <TASK>
 ? commit_tail+0xd7/0x130
 ? drm_atomic_helper_commit+0x126/0x150
 ? drm_atomic_commit+0xa4/0xe0
 ? drm_plane_get_damage_clips.cold+0x1c/0x1c
 ? drm_atomic_helper_dirtyfb+0x19e/0x280
 ? drm_mode_dirtyfb_ioctl+0x10f/0x1e0
 ? drm_mode_getfb2_ioctl+0x2d0/0x2d0
 ? drm_ioctl_kernel+0xc4/0x150
 ? drm_ioctl+0x246/0x3f0
 ? drm_mode_getfb2_ioctl+0x2d0/0x2d0
 ? __x64_sys_ioctl+0x91/0xd0
 ? do_syscall_64+0x60/0xd0
 ? entry_SYSCALL_64_after_hwframe+0x4b/0xb5
 </TASK>
...
rcu: INFO: rcu_sched detected expedited stalls on CPUs/tasks: { 13-.... } 30 jiffies s: 169 root: 0x2000/.
rcu: blocking rcu_node structures (internal RCU debug):
Task dump for CPU 13:
task:X               state:R  running task     stack:    0 pid: 4242 ppid:  4228 flags:0x0000400e
Call Trace:
 <TASK>
 ? memcpy_toio+0x76/0xc0
 ? memcpy_toio+0x1b/0xc0
 ? drm_fb_memcpy_toio+0x76/0xb0
 ? drm_fb_blit_toio+0x75/0x2b0
 ? simpledrm_simple_display_pipe_update+0x132/0x150
 ? drm_atomic_helper_commit_planes+0xb6/0x230
 ? drm_atomic_helper_commit_tail+0x44/0x80
 ? commit_tail+0xd7/0x130
 ? drm_atomic_helper_commit+0x126/0x150
 ? drm_atomic_commit+0xa4/0xe0
 ? drm_plane_get_damage_clips.cold+0x1c/0x1c
 ? drm_atomic_helper_dirtyfb+0x19e/0x280
 ? drm_mode_dirtyfb_ioctl+0x10f/0x1e0
 ? drm_mode_getfb2_ioctl+0x2d0/0x2d0
 ? drm_ioctl_kernel+0xc4/0x150
 ? drm_ioctl+0x246/0x3f0
 ? drm_mode_getfb2_ioctl+0x2d0/0x2d0
 ? __x64_sys_ioctl+0x91/0xd0
 ? do_syscall_64+0x60/0xd0
 ? entry_SYSCALL_64_after_hwframe+0x4b/0xb5
 </TASK>

The problem was added by commit 5e0137612430 ("video/aperture: Disable
and unregister sysfb devices via aperture helpers") to v6.0.3 and does
not exist in the mainline branch.

Why isn't this a problem in Linus's tree?  What commits there cause this
to not be an issue and why can't we just take them instead?

thanks,

greg k-h