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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2009-11-27 17:32:46 +0100
committerIngo Molnar <mingo@elte.hu>2009-12-09 10:03:05 +0100
commitcd29fe6f2637cc2ccbda5ac65f5332d6bf5fa3c6 (patch)
treeb4206012d424a8c0bce1f260d042c678db0602a2 /kernel/sched_fair.c
parentab19cb23313733c55e0517607844b86720b35f5f (diff)
sched: Sanitize fork() handling
Currently we try to do task placement in wake_up_new_task() after we do the load-balance pass in sched_fork(). This yields complicated semantics in that we have to deal with tasks on different RQs and the set_task_cpu() calls in copy_process() and sched_fork() Rename ->task_new() to ->task_fork() and call it from sched_fork() before the balancing, this gives the policy a clear point to place the task. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched_fair.c')
-rw-r--r--kernel/sched_fair.c28
1 files changed, 15 insertions, 13 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 613c1c749677..44ec80ccfa85 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1922,28 +1922,30 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
}
/*
- * Share the fairness runtime between parent and child, thus the
- * total amount of pressure for CPU stays equal - new tasks
- * get a chance to run but frequent forkers are not allowed to
- * monopolize the CPU. Note: the parent runqueue is locked,
- * the child is not running yet.
+ * called on fork with the child task as argument from the parent's context
+ * - child not yet on the tasklist
+ * - preemption disabled
*/
-static void task_new_fair(struct rq *rq, struct task_struct *p)
+static void task_fork_fair(struct task_struct *p)
{
- struct cfs_rq *cfs_rq = task_cfs_rq(p);
+ struct cfs_rq *cfs_rq = task_cfs_rq(current);
struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
int this_cpu = smp_processor_id();
+ struct rq *rq = this_rq();
+ unsigned long flags;
+
+ spin_lock_irqsave(&rq->lock, flags);
- sched_info_queued(p);
+ if (unlikely(task_cpu(p) != this_cpu))
+ __set_task_cpu(p, this_cpu);
update_curr(cfs_rq);
+
if (curr)
se->vruntime = curr->vruntime;
place_entity(cfs_rq, se, 1);
- /* 'curr' will be NULL if the child belongs to a different group */
- if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&
- curr && entity_before(curr, se)) {
+ if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
/*
* Upon rescheduling, sched_class::put_prev_task() will place
* 'current' within the tree based on its new key value.
@@ -1952,7 +1954,7 @@ static void task_new_fair(struct rq *rq, struct task_struct *p)
resched_task(rq->curr);
}
- enqueue_task_fair(rq, p, 0);
+ spin_unlock_irqrestore(&rq->lock, flags);
}
/*
@@ -2052,7 +2054,7 @@ static const struct sched_class fair_sched_class = {
.set_curr_task = set_curr_task_fair,
.task_tick = task_tick_fair,
- .task_new = task_new_fair,
+ .task_fork = task_fork_fair,
.prio_changed = prio_changed_fair,
.switched_to = switched_to_fair,