LITMUS: export CPU stagger offset

Let scheduler plugins inquire stagger offsets.

1 files changed, 21 insertions, 14 deletions

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 3b1936fac0..d6dad226a1 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -583,6 +583,26 @@ static int __init tick_set_quanta_type(char *str)
 }
 __setup("quanta=", tick_set_quanta_type);
 
+u64 cpu_stagger_offset(int cpu)
+{
+        u64 offset = 0;
+        switch (quanta_type) {
+                case LITMUS_ALIGNED_TICKS:
+                        offset = 0;
+                        break;
+                case LITMUS_STAGGERED_TICKS:
+                        offset = ktime_to_ns(tick_period);
+                        do_div(offset, num_possible_cpus());
+                        offset *= cpu;
+                        break;
+                default:
+                        offset = ktime_to_ns(tick_period) >> 1;
+                        do_div(offset, num_possible_cpus());
+                        offset *= cpu;
+        }
+        return offset;
+}
+
 /**
  * tick_setup_sched_timer - setup the tick emulation timer
  */
@@ -603,20 +623,7 @@ void tick_setup_sched_timer(void)
         ts->sched_timer.expires = tick_init_jiffy_update();
 
         /* Offset must be set correctly to achieve desired quanta type. */
-        switch (quanta_type) {
-                case LITMUS_ALIGNED_TICKS:
-                        offset = 0;
-                        break;
-                case LITMUS_STAGGERED_TICKS:
-                        offset = ktime_to_ns(tick_period);
-                        do_div(offset, num_possible_cpus());
-                        offset *= smp_processor_id();
-                        break;
-                default:
-                        offset = ktime_to_ns(tick_period) >> 1;
-                        do_div(offset, num_possible_cpus());
-                        offset *= smp_processor_id();
-        }
+        offset = cpu_stagger_offset(smp_processor_id());
 
         /* Add correct offset to expiration time. */
         ts->sched_timer.expires = ktime_add_ns(ts->sched_timer.expires, offset);