Provided by: systemtap-doc_2.3-1ubuntu1.4_all 

NAME
function::udelay - microsecond delay
SYNOPSIS
udelay(us:long)
ARGUMENTS
us
Number of microseconds to delay.
DESCRIPTION
This function inserts a multi-microsecond busy-delay into a probe handler. It requires guru mode.
SystemTap Tapset Reference March 2016 FUNCTION::UDELAY(3stap)