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SubjectRe: Bug in scheduler when using rt_mutex
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On Wed, 2011-01-19 at 11:38 +0100, Peter Zijlstra wrote:

> Hrm, I think the to bit is not needed with the from thing in place, the
> enqueue from _setprio will already have added min_vruntime


Would lead to something like this:

---
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -8108,6 +8108,8 @@ EXPORT_SYMBOL(__might_sleep);
#ifdef CONFIG_MAGIC_SYSRQ
static void normalize_task(struct rq *rq, struct task_struct *p)
{
+ struct sched_class *prev_class = p->sched_class;
+ int old_prio = p->prio;
int on_rq;

on_rq = p->se.on_rq;
@@ -8118,6 +8120,8 @@ static void normalize_task(struct rq *rq
activate_task(rq, p, 0);
resched_task(rq->curr);
}
+
+ check_class_changed(rq, p, prev_class, old_prio, task_current(rq, p));
}

void normalize_rt_tasks(void)
Index: linux-2.6/kernel/sched_fair.c
===================================================================
--- linux-2.6.orig/kernel/sched_fair.c
+++ linux-2.6/kernel/sched_fair.c
@@ -4066,11 +4066,30 @@ static void prio_changed_fair(struct rq
check_preempt_curr(rq, p, 0);
}

+static void
+switched_from_fair(struct rq *rq, struct task_struct *p, int running)
+{
+ struct sched_entity *se = &p->se;
+ struct cfs_rq *cfs_rq = cfs_rq_of(se);
+
+ /*
+ * Ensure the task's vruntime is normalized, so that when its
+ * switched back to the fair class the enqueue_entity(.flags=0) will
+ * do the right thing.
+ *
+ * If it was on_rq, then the dequeue_entity(.flags=0) will already
+ * have normalized the vruntime, if it was !on_rq, then only when
+ * the task is sleeping will it still have non-normalized vruntime.
+ */
+ if (!se->on_rq && p->state != TASK_RUNNING)
+ se->vruntime -= cfs_rq->min_vruntime;
+}
+
/*
* We switched to the sched_fair class.
*/
-static void switched_to_fair(struct rq *rq, struct task_struct *p,
- int running)
+static void
+switched_to_fair(struct rq *rq, struct task_struct *p, int running)
{
/*
* We were most likely switched from sched_rt, so
@@ -4163,6 +4182,7 @@ static const struct sched_class fair_sch
.task_fork = task_fork_fair,

.prio_changed = prio_changed_fair,
+ .switched_from = switched_from_fair,
.switched_to = switched_to_fair,

.get_rr_interval = get_rr_interval_fair,


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