Re: Does sysrq work over USB?
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@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@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. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Does sysrq work over USB?
On Tue, Nov 16, 2021 at 10:29:00PM +0100, Valentin Vidi?? wrote: > Do you have console=ttyUSB0,... set? What does /proc/consoles say? No, I did not. Now, I have added on a test machine: console=ttyUSB0,9600 console=tty0 to /etc/default/grub and started upgrade-grub and rebooted. I had and I still have: root@gluster-1:~# cat /proc/consoles tty0 -WU (EC p )4:1 However, the command line seems correct and multiple console= are valid [1]: root@gluster-1:~# cat /proc/cmdline BOOT_IMAGE=/vmlinuz-4.19.0-18-amd64 root=/dev/mapper/vg1-root ro console=ttyUSB0,9600 console=tty0 quiet raid0.default_layout=1 It does not seem to be work for some reason. Let's try with one ttyUSB console specification only: does not boot anymore. Does not print anything on ttyUSB0. Had to recover using a grub kernel command line edition at boot time. Any idea? NB: the USB serial port works with cu bidirectionnally once the system is booted, but %break has no effect. [1] https://www.kernel.org/doc/html/latest/admin-guide/serial-console.html ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Does sysrq work over USB?
Hello, I made the following setup work, that is I can send break and '?' (to get the magic sysrq help) or 's' to do an Emergency sync, and the kernel logs it: laptopapu2 USB serial port --- null modem --- ttyS0 internal 16550A (an apu2 is an embedded amd64 computer [4]) As it works, of course MAGIC_SYSRQ is enabled, including for serial ports, and the correct value is in the /proc pseudo-file. It works with the getty enabled or disabled. However, the following does not work to support magic sysrq, although bidirectionnal communication also works with cu [5], with the correct speed set: laptopapu2 USB serial port --- null modem --- USB serial port First, reading documentation, I thought that this would not be possible with USB and only with the internal serial port [1], but then, reading kernel source, it looks it should work with my adapter: Oct 11 14:30:56 apu2-init7 kernel: [9.915105] usb 2-2: pl2303 converter now attached to ttyUSB0 since the driver [2] contains code for magic sysrq, see line 993 for sysrq mode and line 892 for break handling, with implementation in [3] (lines 589-597). I am running Debian buster kernel 4.19.0-18-amd64 on the apu2. Should I abandon all hope to make it work with USB, or should it work? Thank your for any pointers. [1] https://www.kernel.org/doc/Documentation/admin-guide/sysrq.rst "On the serial console (PC style standard serial ports only)" [2] https://github.com/jplozi/linux-4.19/blob/loadbalancing/drivers/usb/serial/pl2303.c [3] https://github.com/jplozi/linux-4.19/blob/loadbalancing/drivers/usb/serial/generic.c [4] https://pcengines.ch/apu2.htm [5] https://linux.die.net/man/1/cu from the days before 2003 where I was doing UUCP cu -l ttyUSB0 -s 9600 ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
