Provided by: systemtap-doc_3.1-3ubuntu0.1_all 

NAME
probe::ioscheduler_trace.plug - Fires when a request queue is plugged;
SYNOPSIS
ioscheduler_trace.plug
VALUES
name
Name of the probe point
rq_queue
request queue
DESCRIPTION
ie, requests in the queue cannot be serviced by block driver.
SEE ALSO
tapset::ioscheduler(3stap)
SystemTap Tapset Reference March 2016 PROBE::IOSCHEDULER_T(3stap)