From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
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..
Tested-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
diff --git a/kernel/sched.c b/kernel/sched.c
index d42992b..e5ad5c0 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -560,18 +560,9 @@ 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 inline
+void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags);
static inline int cpu_of(struct rq *rq)
{
@@ -9400,4 +9391,30 @@ void synchronize_sched_expedited(void)
}
EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
+static inline
+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);
+
+ 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;
+}
+
+
#endif /* #else #ifndef CONFIG_SMP */
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 933f3d1..b8aebc2 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 45bddc0..ddc225b 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)
--
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