Merge tag 'v3.14.43-rt42-lno1' of git://git.linaro.org/people/anders.roxell/linux-rt into linux-linaro-lsk-v3.14-rtlsk-v3.14-15.06-rt

Linux 3.14.43-rt42

Changes since v3.14.39-rt37:
- KVM: lapic: mark LAPIC timer handler as irqsafe
- KVM: use simple waitqueue for vcpu->wq
- hotplug: Use set_cpus_allowed_ptr() in sync_unplug_thread()
- rt, nohz_full: fix nohz_full for PREEMPT_RT_FULL
- kernel/irq_work: fix no_hz deadlock

* tag 'v3.14.43-rt42-lno1' of git://git.linaro.org/people/anders.roxell/linux-rt: (360 commits)
  Linux 3.14.43-rt42 REBASE
  rt, nohz_full: fix nohz_full for PREEMPT_RT_FULL
  hotplug: Use set_cpus_allowed_ptr() in sync_unplug_thread()
  KVM: use simple waitqueue for vcpu->wq
  KVM: lapic: mark LAPIC timer handler as irqsafe
  kernel/irq_work: fix no_hz deadlock
  netpoll: guard the access to dev->npinfo with rcu_read_lock/unlock_bh() for CONFIG_PREEMPT_RT_FULL=y
  Revert "timers: do not raise softirq unconditionally"
  fs,btrfs: fix rt deadlock on extent_buffer->lock
  staging: Mark rtl8821ae as broken
  timers: Reduce future __run_timers() latency for first add to empty list
  timers: Reduce future __run_timers() latency for newly emptied list
  timers: Reduce __run_timers() latency for empty list
  timers: Track total number of timers in list
  fs/aio: simple simple work
  lockdep: selftest: fix warnings due to missing PREEMPT_RT conditionals
  thermal: Defer thermal wakups to threads
  locking: ww_mutex: fix ww_mutex vs self-deadlock
  Revert "rwsem-rt: Do not allow readers to nest"
  sunrpc: make svc_xprt_do_enqueue() use get_cpu_light()
  ...

1 files changed, 23 insertions, 6 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 883669d3e293..71c0bb1cdeb0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -696,17 +696,34 @@ static inline bool got_nohz_idle_kick(void)
 #endif /* CONFIG_NO_HZ_COMMON */
 
 #ifdef CONFIG_NO_HZ_FULL
+
+static int ksoftirqd_running(void)
+{
+	struct task_struct *softirqd;
+
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
+		return 0;
+	softirqd = this_cpu_ksoftirqd();
+	if (softirqd && softirqd->on_rq)
+		return 1;
+	return 0;
+}
+
 bool sched_can_stop_tick(void)
 {
-       struct rq *rq;
+	struct rq *rq;
 
-       rq = this_rq();
+	rq = this_rq();
 
-       /* Make sure rq->nr_running update is visible after the IPI */
-       smp_rmb();
+	/* Make sure rq->nr_running update is visible after the IPI */
+	smp_rmb();
 
-       /* More than one running task need preemption */
-       if (rq->nr_running > 1)
+	/*
+	 * More than one running task need preemption
+	 *
+	 * NOTE, RT: if ksoftirqd is awake, subtract it.
+	 */
+	if (rq->nr_running - ksoftirqd_running() > 1)
                return false;
 
        return true;