* Steven Rostedt | 2015-05-13 12:34:27 [-0400]:

Found the bug. The above actually changes the code
for !CONFIG_PREEMPT_RT_FULL. You still need to keep that

if (in_irq())

check, otherwise you can call irq_work_tick() from softirq in non RT
configs, which talking to Peter Zijlstra, is a no no.

Note, my tests were failing on CONFIG_PREEMPT_LL (low latency).

This was removed by mistake. Obviously. I am adding the chunk back:

--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c

@@ -1450,7 +1450,8 @@ void update_process_times(int user_tick)
 	run_local_timers();
 	rcu_check_callbacks(user_tick);
 #if defined(CONFIG_IRQ_WORK) && !defined(CONFIG_PREEMPT_RT_FULL)
-	irq_work_tick();
+	if (in_irq())
+		irq_work_tick();
 #endif
 	run_posix_cpu_timers(p);
 }

Sebastian