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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2010-10-31 12:37:04 +0100
committerIngo Molnar <mingo@elte.hu>2010-11-11 14:37:23 +0100
commit1e5a74059f9059d330744eac84873b1b99657008 (patch)
treef32f8ac76d5a6c49c1b4cd8f83155af00007fac0 /kernel
parent2d46709082c062cae7cce1a15f8cd4cd81b92d88 (diff)
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sched: Fix cross-sched-class wakeup preemption
Instead of dealing with sched classes inside each check_preempt_curr() implementation, pull out this logic into the generic wakeup preemption path. This fixes a hang in KVM (and others) where we are waiting for the stop machine thread to run ... Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de> Tested-by: Marcelo Tosatti <mtosatti@redhat.com> Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1288891946.2039.31.camel@laptop> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched.c37
-rw-r--r--kernel/sched_fair.c6
-rw-r--r--kernel/sched_stoptask.c2
3 files changed, 27 insertions, 18 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 36a088018fe..dc91a4d09ac 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -560,18 +560,8 @@ struct rq {
static DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
-static inline
-void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
-{
- rq->curr->sched_class->check_preempt_curr(rq, p, flags);
- /*
- * A queue event has occurred, and we're going to schedule. In
- * this case, we can save a useless back to back clock update.
- */
- if (test_tsk_need_resched(p))
- rq->skip_clock_update = 1;
-}
+static void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags);
static inline int cpu_of(struct rq *rq)
{
@@ -2118,6 +2108,31 @@ static inline void check_class_changed(struct rq *rq, struct task_struct *p,
p->sched_class->prio_changed(rq, p, oldprio, running);
}
+static void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
+{
+ const struct sched_class *class;
+
+ if (p->sched_class == rq->curr->sched_class) {
+ rq->curr->sched_class->check_preempt_curr(rq, p, flags);
+ } else {
+ for_each_class(class) {
+ if (class == rq->curr->sched_class)
+ break;
+ if (class == p->sched_class) {
+ resched_task(rq->curr);
+ break;
+ }
+ }
+ }
+
+ /*
+ * A queue event has occurred, and we're going to schedule. In
+ * this case, we can save a useless back to back clock update.
+ */
+ if (test_tsk_need_resched(rq->curr))
+ rq->skip_clock_update = 1;
+}
+
#ifdef CONFIG_SMP
/*
* Is this task likely cache-hot:
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 034c4f410b3..52ab113d8bb 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1654,12 +1654,6 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
int scale = cfs_rq->nr_running >= sched_nr_latency;
- if (unlikely(rt_prio(p->prio)))
- goto preempt;
-
- if (unlikely(p->sched_class != &fair_sched_class))
- return;
-
if (unlikely(se == pse))
return;
diff --git a/kernel/sched_stoptask.c b/kernel/sched_stoptask.c
index 755483b2a2a..2bf6b47058c 100644
--- a/kernel/sched_stoptask.c
+++ b/kernel/sched_stoptask.c
@@ -19,7 +19,7 @@ select_task_rq_stop(struct rq *rq, struct task_struct *p,
static void
check_preempt_curr_stop(struct rq *rq, struct task_struct *p, int flags)
{
- resched_task(rq->curr); /* we preempt everything */
+ /* we're never preempted */
}
static struct task_struct *pick_next_task_stop(struct rq *rq)