Poor-man's Ftrace is a live printk function tracer.  It does not handle
concurrency well, whether that is interleaved IRQs or especially parallelism.
Everything gets printed at the same time, and shares the same global
indentation variable.  Still, it works reasonably well for IRQs, ktasks, and
syscalls.

Careful using this on certain devices in k/d/dev/, like acpi and console.  One
of the devs locks up if you try to print.

I usually turn off the 'print' bool in kdebug.c for booting, then turn it on
via 'kfunc toggle_print_func'.

To spatch the networking code, try something like:

$ for i in kern/src/net kern/drivers/net kern/drivers/dev/ether.c; do
    spatch --sp-file scripts/spatch/poor-ftrace.cocci  --in-place $i; done