Does sysrq work over USB?

[Marc SCHAEFER]

Hello,

On Sun, Nov 21, 2021 at 07:07:33PM +0100, Valentin Vidi?? wrote:
> I tried and it doesn't work for me either, but the problem is most
> likely missing CONFIG_USB_SERIAL_CONSOLE=y option in the kernel build:
> 
>   https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=868352

Yes,

with a kernel recompiled with those options and grub configured,
I get:

CONFIG_USB=y
CONFIG_USB_SERIAL=y
CONFIG_USB_SERIAL_CONSOLE=y
CONFIG_U_SERIAL_CONSOLE=y

I get:

   root at gluster-1:~# cat /proc/consoles 
   tty0                 -WU (EC p  )    4:1
   ttyUSB0              -W- (E  p  )  188:0

and I can then do sysrq from USB:
   schaefer at acer-1:~$ cu -l ttyUSB0 -s 9600
   Connected.
   ~%break
   [ 1633.701624] sysrq: HELP : loglevel(0-9) reboot(b) crash(c)
   terminate-all-tasks(e) memory-full-oom-kill(f) kill-all-tasks(i)
   thaw-filesystems(j) sak(k) show-backtrace-all-active-cpus(l)
   show-memory-usage(m) nice-all-RT-tasks(n) poweroff(o) show-registers(p)
   show-all-timers(q) unraw(r) sync(s) show-task-states(t) unmount(u)
   force-fb(V) show-blocked-tasks(w) dump-ftrace-buffer(z) 
   
Thank you for your help: I have now a way to make it work.