Apr 20 10:36:55 rd4 kernel: [23249.017661] 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) 

# Show stack traces for all CPUs
$ echo l > /proc/sysrq-trigger

# show task states
$ echo t > /proc/sysrq-trigger

# trigger a crash
$ echo c > /proc/sysrq-trigger