Provided by: systemtap-doc_2.9-2ubuntu2_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.
SEE ALSO
tapset::guru-delay(3stap)
SystemTap Tapset Reference April 2016 FUNCTION::UDELAY(3stap)