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[PATCH RT 03/17] preempt-lazy: Add the lazy-preemption check to preempt_schedule()

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3.14.61-rt64-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Probably in the rebase onto v4.1 this check got moved into less commonly used
preempt_schedule_notrace(). This patch ensures that both functions use it.

Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/sched/core.c | 34 ++++++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index edacb6d1d2bf..157ef7f121fb 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2998,6 +2998,30 @@ void __sched schedule_preempt_disabled(void)
 	preempt_disable();
 }
 
+#ifdef CONFIG_PREEMPT_LAZY
+/*
+ * If TIF_NEED_RESCHED is then we allow to be scheduled away since this is
+ * set by a RT task. Oterwise we try to avoid beeing scheduled out as long as
+ * preempt_lazy_count counter >0.
+ */
+static int preemptible_lazy(void)
+{
+	if (test_thread_flag(TIF_NEED_RESCHED))
+		return 1;
+	if (current_thread_info()->preempt_lazy_count)
+		return 0;
+	return 1;
+}
+
+#else
+
+static int preemptible_lazy(void)
+{
+	return 1;
+}
+
+#endif
+
 #ifdef CONFIG_PREEMPT
 /*
  * this is the entry point to schedule() from in-kernel preemption
@@ -3012,15 +3036,9 @@ asmlinkage void __sched notrace preempt_schedule(void)
 	 */
 	if (likely(!preemptible()))
 		return;
-
-#ifdef CONFIG_PREEMPT_LAZY
-	/*
-	 * Check for lazy preemption
-	 */
-	if (current_thread_info()->preempt_lazy_count &&
-			!test_thread_flag(TIF_NEED_RESCHED))
+	if (!preemptible_lazy())
 		return;
-#endif
+
 	do {
 		__preempt_count_add(PREEMPT_ACTIVE);
 		/*
-- 
2.7.0

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[PATCH RT 00/17] Linux 3.14.61-rt64-rc1 Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 16:50 +0100
  [PATCH RT 04/17] softirq: split timer softirqs out of ksoftirqd Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 16:50 +0100
  [PATCH RT 08/17] kernel: migrate_disable() do fastpath in atomic & irqs-off Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 16:50 +0100
  [PATCH RT 06/17] latencyhist: disable jump-labels Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 16:50 +0100
  [PATCH RT 10/17] kernel/stop_machine: partly revert "stop_machine: Use raw spinlocks" Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 16:50 +0100
  [PATCH RT 14/17] f2fs: Mutex cant be used by down_write_nest_lock() Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 16:50 +0100
  [PATCH RT 01/17] ptrace: dont open IRQs in ptrace_freeze_traced() too early Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 16:50 +0100
  [PATCH RT 15/17] rcu/torture: Comment out rcu_bh ops on PREEMPT_RT_FULL Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 16:50 +0100
  [PATCH RT 09/17] kernel: softirq: unlock with irqs on Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 16:50 +0100
  [PATCH RT 05/17] net: provide a way to delegate processing a softirq to ksoftirqd Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 16:50 +0100
  [PATCH RT 03/17] preempt-lazy: Add the lazy-preemption check to preempt_schedule() Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 17:00 +0100
  [PATCH RT 11/17] sched,rt: __always_inline preemptible_lazy() Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 17:10 +0100
  [PATCH RT 02/17] net: move xmit_recursion to per-task variable on -RT Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 17:10 +0100
  [PATCH RT 13/17] trace: Use rcuidle version for preemptoff_hist trace point Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 17:10 +0100
  [PATCH RT 12/17] drm,radeon,i915: Use preempt_disable/enable_rt() where recommended Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 17:10 +0100
  [PATCH RT 16/17] kernel: sched: Fix preempt_disable_ip recodring for preempt_disable() Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 17:10 +0100
  [PATCH RT 07/17] arm64: replace read_lock to rcu lock in call_step_hook Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 17:10 +0100
    Re: [PATCH RT 07/17] arm64: replace read_lock to rcu lock in  call_step_hook Pratyush Anand <panand@redhat.com> - 2016-03-03 05:30 +0100
      Re: [PATCH RT 07/17] arm64: replace read_lock to rcu lock in  call_step_hook Steven Rostedt <rostedt@goodmis.org> - 2016-03-03 15:20 +0100
        Re: [PATCH RT 07/17] arm64: replace read_lock to rcu lock in  call_step_hook Steven Rostedt <rostedt@goodmis.org> - 2016-03-03 15:30 +0100
  [PATCH RT 17/17] Linux 3.14.61-rt64-rc1 Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 17:10 +0100

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