// scheduler tapset
// Copyright (C) 2006 Intel Corporation.
//
// This file is part of systemtap, and is free software.  You can
// redistribute it and/or modify it under the terms of the GNU General
// Public License (GPL); either version 2, or (at your option) any
// later version.


function __is_idle:long()
%{
    /* Ways to detect idle-ness:
     * - pid() or tid() == 0
     * - current == current->parent
     * - current == this_rq()->idle
     * - others?
     */
    THIS->__retvalue = (current->pid == 0);
%}


/* probe scheduler.cpu_off
 *
 *  Fires when a process is about to stop running on a cpu.
 *
 * Context:
 *  The process leaving the cpu.
 *
 * Arguments:
 *  task_prev - the process leaving the cpu (same as current)
 *  task_next - the process replacing current
 *  idle - boolean indicating whether current is the idle process
 */
probe scheduler.cpu_off
    = kernel.inline("context_switch")
{
    task_prev = $prev
    task_next = $next
    idle = __is_idle()
}


/* probe scheduler.cpu_on
 *
 *  Fires when a process is beginning execution on a cpu.
 *
 * Context:
 *  The resuming process.
 *
 * Arguments:
 *  task_prev - the process that was previously running on this cpu.
 *  idle - boolean indicating whether current is the idle process
 */
probe scheduler.cpu_on
    = kernel.inline("finish_task_switch")
{
    task_prev = $prev
    idle = __is_idle()
}


/* probe scheduler.tick
 *
 *  Fires on the schedulers internal tick, when a processes timeslice
 *  accounting is updated.
 *
 * Context:
 *  The process whose accounting will be updated.
 *
 * Arguments:
 *  idle - boolean indicating whether current is the idle process
 */
probe scheduler.tick = kernel.function("scheduler_tick")
{
    idle = __is_idle()
}


/* probe scheduler.migrate
 *
 *  Fires whenever a task is moved to a different cpu's runqueue.
 *
 * Context:
 *  Unknown (sometimes migration thread, sometimes cpu_to)
 *
 * Arguments:
 *  task - the process that is being migrated
 *  cpu_from - the cpu that is losing the task
 *  cpu_to - the cpu that is claiming the task
 */
probe scheduler.migrate = kernel.inline("pull_task") {
    task = $p
    cpu_from = $p->thread_info->cpu
    cpu_to = $this_cpu
}


/* probe scheduler.balance
 *
 *  Fires when a cpu attempts to find more work.
 *
 * Context:
 *  The cpu looking for more work.
 */
probe scheduler.balance = kernel.inline("idle_balance") {}