On Mon, 2016-01-18 at 21:18 +0100, Sebastian Andrzej Siewior wrote:

quoted

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c

@@ -3542,6 +3542,15 @@ asmlinkage __visible void __sched notrac

	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))
+		return;
+#endif
+

And this is a new piece. So you forbid that tasks leave the CPU if
lazy_count > 0. Let me look closed why this is happening and if this is
v4.1 … v4.4 or not.

That check wants a !rt_task(current) qualifier anyway.

	-Mike
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