Slackware64 -current: blank screen and computer lockup on startx, now fixed or worked around

Slackware64 -current: after updates, blank screen and computer lockup on startx, now fixed or worked around

- On Feb 5, I started my system having last updated Jan 24, except for the kernel: I was still on 6.6.11 (which was available Jan 10.)

- After running Feb 4 updates except kernel (still on 6.6.11, although 6.6.15 was available) and rebooting, I got a blank screen whether trying to launch KDE, Xfce or Fluxbox. For the first 10 seconds or so, it was possible to open another tty. Waiting any longer than that, and not only did the screen go blank, it froze and everything was unresponsive: cursor wouldn't move, Ctrl-Alt-Bkspc did nothing and I couldn't switch to another tty. I could only hard shutdown.

- I multiboot with Slackware64 15.0 on the same drive, and everything has been working well there.

- On -current, the source of the problem seems to be similar to a blank screen problem that showed up after Dec 2020 updates, tied to a kernel 5.4.x update that was fixed in a later 5.4.x (I think) update. I don't think it has the entirely same root cause(s), because back then IIRC I got a blank screen but could still open other ttys, where this time I got a blank screen and, after a few seconds, a complete lockup.

- Over the past couple of weeks, after trying a bunch of things to try to fix this, the following works, for now, with caveat below*:
LQ post [SOLVED] vtown startx not working started by @Chuck56

https://www.linuxquestions.org/quest...3/#post6191959

I created 2 files in /etc/modprobe.d, then rebooted

/etc/modprobe.d/amdgpu.conf
Code:options amdgpu si_support=1
options amdgpu cik_support=1/etc/modprobe.d/radeon.conf
Code:options radeon si_support=0
options radeon cik_support=0If this affects you, read to the end of the thread, for two reasons:
1) @Chuck56 refined his steps
2) I had to reverse the fix*

*Caveat: I doubt the durability of this fix, since later in December 2020, after the kernel was upgraded to 5.10.x, that included a fix for the original problem, I got a blank screen again. I fixed that by disabling the /etc/modprobe.d/amdgpu.conf and /etc/modprobe.d/radeon.conf files I had created earlier. @Chuck56's final post in that thread might be the way to go for a more durable fix.

_____

A little more background:

1) After getting a blank screen after Feb 4 updates except for kernel, still on 6.6.11:

Code:$ inxi -G
Graphics:
Device-1: AMD Kaveri [Radeon R7 Graphics] driver: radeon v: kernel
Display: server: X.org v: 1.21.1.11 with: Xwayland v: 23.2.4 driver: X: loaded: radeon
unloaded: fbdev,modesetting,vesa dri: radeonsi gpu: radeon tty: 240x67 resolution: 1920x1080
API: EGL v: 1.5 drivers: radeonsi,swrast platforms: gbm,surfaceless,device
API: OpenGL Message: GL data unavailable in console. Try -G --display
API: Vulkan v: 1.3.268 drivers: llvmpipe surfaces: N/AXorg.1.log last lines where errors first show up, after $ startx and letting the computer run until it locked up

Code:[ 258.415] (EE)
[ 258.415] (EE) Backtrace:
[ 258.443] (EE) 0: /usr/libexec/Xorg (OsLookupColor+0x149) [0x5a2be9]
[ 258.463] (EE) 1: /lib64/libc.so.6 (__sigaction+0x40) [0x7fafa6642eb0]
[ 258.478] (EE) 2: /usr/lib64/dri/radeonsi_dri.so (radeon_drm_winsys_create+0x2845) [0x7fafa418b5e5]
[ 258.479] (EE) 3: /usr/lib64/dri/radeonsi_dri.so (radeon_drm_winsys_create+0x471d) [0x7fafa418d4bd]
[ 258.480] (EE) 4: /usr/lib64/dri/radeonsi_dri.so (nouveau_drm_screen_create+0x26f116) [0x7fafa45c00e6]
[ 258.481] (EE) 5: /usr/lib64/dri/radeonsi_dri.so (nouveau_drm_screen_create+0x26f2a9) [0x7fafa45c0279]
[ 258.481] (EE) 6: /usr/lib64/dri/radeonsi_dri.so (radeon_drm_winsys_create+0x3a7a) [0x7fafa418c81a]
[ 258.482] (EE) 7: /usr/lib64/dri/radeonsi_dri.so (radeon_drm_winsys_create+0x12ccb3) [0x7fafa42b5a53]
[ 258.483] (EE) 8: /usr/lib64/dri/radeonsi_dri.so (radeon_drm_winsys_create+0xf8b45) [0x7fafa42818e5]
[ 258.483] (EE) 9: /usr/lib64/dri/radeonsi_dri.so (radeon_drm_winsys_create+0xf992a) [0x7fafa42826ca]
[ 258.483] (EE) 10: /usr/lib64/dri/radeonsi_dri.so (radeon_drm_winsys_create+0xf7569) [0x7fafa4280309]
[ 258.484] (EE) 11: /usr/lib64/dri/radeonsi_dri.so (nouveau_drm_screen_create+0x27c4cd) [0x7fafa45cd49d]
[ 258.484] (EE) 12: /usr/lib64/dri/radeonsi_dri.so (__driDriverGetExtensions_zink+0xb3fa1) [0x7fafa3b5c381]
[ 258.485] (EE) 13: /usr/lib64/dri/radeonsi_dri.so (__driDriverGetExtensions_zink+0x8814d) [0x7fafa3b3052d]
[ 258.485] (EE) 14: /usr/lib64/dri/radeonsi_dri.so (__driDriverGetExtensions_zink+0x8b5cd) [0x7fafa3b339ad]
[ 258.485] (EE) 15: /usr/lib64/dri/radeonsi_dri.so (__driDriverGetExtensions_zink+0x91758) [0x7fafa3b39b38]
[ 258.485] (EE) 16: /usr/lib64/xorg/modules/libglamoregl.so (glamor_create_gc+0xfa82) [0x7fafa38bb782]
[ 258.486] (EE) 17: /usr/lib64/xorg/modules/libglamoregl.so (glamor_create_gc+0xfcdb) [0x7fafa38bb9db]
[ 258.486] (EE) 18: /usr/lib64/xorg/modules/libglamoregl.so (glamor_create_gc+0x2a0e) [0x7fafa38ae70e]
[ 258.486] (EE) 19: /usr/libexec/Xorg (DamageRegionAppend+0x3480) [0x5178a0]
[ 258.486] (EE) 20: /usr/libexec/Xorg (SendGraphicsExpose+0xec3) [0x43fb93]
[ 258.486] (EE) 21: /usr/libexec/Xorg (SendErrorToClient+0x3b4) [0x442f94]
[ 258.487] (EE) 22: /usr/libexec/Xorg (InitFonts+0x3ac) [0x446e0c]
[ 258.487] (EE) 23: /lib64/libc.so.6 (__libc_start_call_main+0x67) [0x7fafa6629b77]
[ 258.488] (EE) 24: /lib64/libc.so.6 (__libc_start_main+0x85) [0x7fafa6629c35]
[ 258.488] (EE) 25: /usr/libexec/Xorg (_start+0x21) [0x431121]
[ 258.488] (EE)
[ 258.488] (EE) Segmentation fault at address 0x40
[ 258.488] (EE)
Fatal server error:
[ 258.488] (EE) Caught signal 11 (Segmentation fault). Server aborting
[ 258.488] (EE)
[ 258.488] (EE)
Please consult the The X.Org Foundation support
at http://wiki.x.org
for help.
[ 258.488] (EE) Please also check the log file at "/var/log/Xorg.1.log" for additional information.
[ 258.488] (EE)
[ 258.488] (II) AIGLX: Suspending AIGLX clients for VT switch2) Ran updates, including kernel to 6.6.16, which I'm still on. Same problem, although after updates and trying a bunch of other things to fix this, I got this message on screen (summarized): KDE Crash Handler closed unexpectedly... Executable drkonqi... Segmentation fault (11)

3) Add /etc/modprobe.d/amdgpu.conf and /etc/modprobe.d/radeon.conf as above. Reboot. Success!

Code:$ inxi -G
Graphics:
Device-1: AMD Kaveri [Radeon R7 Graphics] driver: amdgpu v: kernel
Display: server: X.Org v: 21.1.11 with: Xwayland v: 23.2.4 driver: X:
loaded: amdgpu unloaded: fbdev,modesetting,vesa dri: radeonsi gpu: amdgpu
resolution: 1920x1080~60Hz
API: EGL v: 1.5 drivers: kms_swrast,radeonsi,swrast
platforms: gbm,x11,surfaceless,device
API: OpenGL v: 4.6 vendor: amd mesa v: 24.0.1 renderer: AMD Radeon R7
Graphics (radeonsi kaveri LLVM 17.0.6 DRM 3.54 6.6.16)
API: Vulkan v: 1.3.268 drivers: radv,llvmpipe surfaces: xcb,xlibXorg.0.log: no (EE)