Nathan Lynch [off-list ref] writes:

Alternatively, sys_rtas() could be refactored into locking and
non-locking paths, e.g.

static long __do_sys_rtas(struct rtas_function *func)
{
	// [ ... acquire rtas_lock, enter RTAS, fetch any error etc ... ]
}

Of course this conflicts with the code generated by SYSCALL_DEFINE1(rtas), so
a different function name would be needed here.