I am having trouble sending sysrq commands over USB serial, and I'm not sure what else to check.
I have two identical machines, each with usb-to-serial adapters, joined by a null modem adapter. One runs an agetty, the other minicom. I can log in over the agetty as a user and it works as expected, until I try to send a sysrq.
To send a break in minicom, I type [Ctrl]+[a] then [f]. Then I type the character [m] to do a test. I expect to see memory information print to screen, or at least show up in dmesg. Instead I only see the letter m on my shell.
I'm using 115200, 8N1, VT102. I can echo m > /proc/sysctl-trigger, and dmesg shows that the sysrq was received when initiated via the procfs interface. But not over serial, and that's what I need.