2007-07-09 12:51:58 -04:00
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/*
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* idle-task scheduling class.
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*
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* (NOTE: these are not related to SCHED_IDLE tasks which are
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* handled in sched_fair.c)
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*/
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2008-01-25 15:08:09 -05:00
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#ifdef CONFIG_SMP
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2009-09-14 13:55:44 -04:00
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static int select_task_rq_idle(struct task_struct *p, int sd_flag, int flags)
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2008-01-25 15:08:09 -05:00
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{
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return task_cpu(p); /* IDLE tasks as never migrated */
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}
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#endif /* CONFIG_SMP */
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2007-07-09 12:51:58 -04:00
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/*
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* Idle tasks are unconditionally rescheduled:
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*/
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2009-09-14 13:55:44 -04:00
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static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
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2007-07-09 12:51:58 -04:00
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{
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resched_task(rq->idle);
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}
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2007-08-09 05:16:48 -04:00
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static struct task_struct *pick_next_task_idle(struct rq *rq)
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2007-07-09 12:51:58 -04:00
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{
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schedstat_inc(rq, sched_goidle);
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2009-04-11 04:43:41 -04:00
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/* adjust the active tasks as we might go into a long sleep */
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calc_load_account_active(rq);
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2007-07-09 12:51:58 -04:00
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return rq->idle;
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}
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/*
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* It is not legal to sleep in the idle task - print a warning
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* message if some code attempts to do it:
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*/
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static void
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2007-08-09 05:16:48 -04:00
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dequeue_task_idle(struct rq *rq, struct task_struct *p, int sleep)
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2007-07-09 12:51:58 -04:00
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{
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2009-11-17 08:28:38 -05:00
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raw_spin_unlock_irq(&rq->lock);
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2009-12-20 08:23:57 -05:00
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printk(KERN_ERR "bad: scheduling from the idle thread!\n");
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2007-07-09 12:51:58 -04:00
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dump_stack();
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2009-11-17 08:28:38 -05:00
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raw_spin_lock_irq(&rq->lock);
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2007-07-09 12:51:58 -04:00
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}
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2007-08-09 05:16:49 -04:00
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static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
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2007-07-09 12:51:58 -04:00
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{
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}
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2007-10-24 12:23:51 -04:00
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#ifdef CONFIG_SMP
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sched: simplify move_tasks()
The move_tasks() function is currently multiplexed with two distinct
capabilities:
1. attempt to move a specified amount of weighted load from one run
queue to another; and
2. attempt to move a specified number of tasks from one run queue to
another.
The first of these capabilities is used in two places, load_balance()
and load_balance_idle(), and in both of these cases the return value of
move_tasks() is used purely to decide if tasks/load were moved and no
notice of the actual number of tasks moved is taken.
The second capability is used in exactly one place,
active_load_balance(), to attempt to move exactly one task and, as
before, the return value is only used as an indicator of success or failure.
This multiplexing of sched_task() was introduced, by me, as part of the
smpnice patches and was motivated by the fact that the alternative, one
function to move specified load and one to move a single task, would
have led to two functions of roughly the same complexity as the old
move_tasks() (or the new balance_tasks()). However, the new modular
design of the new CFS scheduler allows a simpler solution to be adopted
and this patch addresses that solution by:
1. adding a new function, move_one_task(), to be used by
active_load_balance(); and
2. making move_tasks() a single purpose function that tries to move a
specified weighted load and returns 1 for success and 0 for failure.
One of the consequences of these changes is that neither move_one_task()
or the new move_tasks() care how many tasks sched_class.load_balance()
moves and this enables its interface to be simplified by returning the
amount of load moved as its result and removing the load_moved pointer
from the argument list. This helps simplify the new move_tasks() and
slightly reduces the amount of work done in each of
sched_class.load_balance()'s implementations.
Further simplification, e.g. changes to balance_tasks(), are possible
but (slightly) complicated by the special needs of load_balance_fair()
so I've left them to a later patch (if this one gets accepted).
NB Since move_tasks() gets called with two run queue locks held even
small reductions in overhead are worthwhile.
[ mingo@elte.hu ]
this change also reduces code size nicely:
text data bss dec hex filename
39216 3618 24 42858 a76a sched.o.before
39173 3618 24 42815 a73f sched.o.after
Signed-off-by: Peter Williams <pwil3058@bigpond.net.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2007-08-09 05:16:46 -04:00
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static unsigned long
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2007-07-09 12:51:58 -04:00
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load_balance_idle(struct rq *this_rq, int this_cpu, struct rq *busiest,
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2007-10-24 12:23:51 -04:00
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unsigned long max_load_move,
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struct sched_domain *sd, enum cpu_idle_type idle,
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int *all_pinned, int *this_best_prio)
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{
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return 0;
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}
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static int
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move_one_task_idle(struct rq *this_rq, int this_cpu, struct rq *busiest,
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struct sched_domain *sd, enum cpu_idle_type idle)
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2007-07-09 12:51:58 -04:00
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{
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return 0;
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}
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2007-10-24 12:23:51 -04:00
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#endif
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2007-07-09 12:51:58 -04:00
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2008-01-25 15:08:29 -05:00
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static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
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2007-07-09 12:51:58 -04:00
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{
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}
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2007-10-15 11:00:08 -04:00
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static void set_curr_task_idle(struct rq *rq)
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{
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}
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2008-01-25 15:08:22 -05:00
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static void switched_to_idle(struct rq *rq, struct task_struct *p,
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int running)
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{
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/* Can this actually happen?? */
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if (running)
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resched_task(rq->curr);
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else
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2008-09-20 17:38:02 -04:00
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check_preempt_curr(rq, p, 0);
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2008-01-25 15:08:22 -05:00
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}
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static void prio_changed_idle(struct rq *rq, struct task_struct *p,
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int oldprio, int running)
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{
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/* This can happen for hot plug CPUS */
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/*
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* Reschedule if we are currently running on this runqueue and
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* our priority decreased, or if we are not currently running on
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* this runqueue and our priority is higher than the current's
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*/
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if (running) {
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if (p->prio > oldprio)
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resched_task(rq->curr);
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} else
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2008-09-20 17:38:02 -04:00
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check_preempt_curr(rq, p, 0);
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2008-01-25 15:08:22 -05:00
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}
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2009-12-09 03:32:03 -05:00
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unsigned int get_rr_interval_idle(struct rq *rq, struct task_struct *task)
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2009-09-20 21:31:53 -04:00
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{
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return 0;
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}
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2007-07-09 12:51:58 -04:00
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/*
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* Simple, special scheduling class for the per-CPU idle tasks:
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*/
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2008-04-25 13:53:13 -04:00
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static const struct sched_class idle_sched_class = {
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2007-10-15 11:00:12 -04:00
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/* .next is NULL */
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2007-07-09 12:51:58 -04:00
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/* no enqueue/yield_task for idle tasks */
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/* dequeue is not valid, we print a debug message there: */
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.dequeue_task = dequeue_task_idle,
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.check_preempt_curr = check_preempt_curr_idle,
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.pick_next_task = pick_next_task_idle,
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.put_prev_task = put_prev_task_idle,
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2007-10-24 12:23:51 -04:00
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#ifdef CONFIG_SMP
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2008-10-22 03:25:26 -04:00
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.select_task_rq = select_task_rq_idle,
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2007-07-09 12:51:58 -04:00
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.load_balance = load_balance_idle,
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2007-10-24 12:23:51 -04:00
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.move_one_task = move_one_task_idle,
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2007-10-24 12:23:51 -04:00
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#endif
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2007-07-09 12:51:58 -04:00
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2007-10-15 11:00:08 -04:00
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.set_curr_task = set_curr_task_idle,
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2007-07-09 12:51:58 -04:00
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.task_tick = task_tick_idle,
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2008-01-25 15:08:22 -05:00
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2009-09-20 21:31:53 -04:00
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.get_rr_interval = get_rr_interval_idle,
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2008-01-25 15:08:22 -05:00
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.prio_changed = prio_changed_idle,
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.switched_to = switched_to_idle,
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2007-07-09 12:51:58 -04:00
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/* no .task_new for idle tasks */
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};
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