clear_trace() { # reset trace output
    echo > trace
}

disable_tracing() { # stop trace recording
    echo 0 > tracing_on
}

enable_tracing() { # start trace recording
    echo 1 > tracing_on
}

reset_tracer() { # reset the current tracer
    echo nop > current_tracer
}

reset_trigger() { # reset all current setting triggers
    grep -v ^# events/*/*/trigger |
    while read line; do
        cmd=`echo $line | cut -f2- -d: | cut -f1 -d" "`
	echo "!$cmd" > `echo $line | cut -f1 -d:`
    done
}

reset_events_filter() { # reset all current setting filters
    grep -v ^none events/*/*/filter |
    while read line; do
	echo 0 > `echo $line | cut -f1 -d:`
    done
}

reset_ftrace_filter() { # reset all triggers in set_ftrace_filter
    echo > set_ftrace_filter
    grep -v '^#' set_ftrace_filter | while read t; do
	tr=`echo $t | cut -d: -f2`
	if [ "$tr" == "" ]; then
	    continue
	fi
	if [ $tr == "enable_event" -o $tr == "disable_event" ]; then
	    tr=`echo $t | cut -d: -f1-4`
	    limit=`echo $t | cut -d: -f5`
	else
	    tr=`echo $t | cut -d: -f1-2`
	    limit=`echo $t | cut -d: -f3`
	fi
	if [ "$limit" != "unlimited" ]; then
	    tr="$tr:$limit"
	fi
	echo "!$tr" > set_ftrace_filter
    done
}

disable_events() {
    echo 0 > events/enable
}

initialize_ftrace() { # Reset ftrace to initial-state
# As the initial state, ftrace will be set to nop tracer,
# no events, no triggers, no filters, no function filters,
# no probes, and tracing on.
    disable_tracing
    reset_tracer
    reset_trigger
    reset_events_filter
    disable_events
    echo > set_event_pid	# event tracer is always on
    [ -f set_ftrace_filter ] && echo | tee set_ftrace_*
    [ -f set_graph_function ] && echo | tee set_graph_*
    [ -f stack_trace_filter ] && echo > stack_trace_filter
    [ -f kprobe_events ] && echo > kprobe_events
    [ -f uprobe_events ] && echo > uprobe_events
    enable_tracing
}