Integrate ft_irq_fired() with Linux

This patch hooks up Feather-Trace's ft_irq_fired() handler with
Linux's interrupt handling infrastructure.

IRQ tracing: ft_irq_fired() only if irq_enter() was skipped

On x86, the rescheduling IPI path already calls irq_enter(), which
calls ft_irq_fired(), so we don't have to do it again.

IRQ tracing: don't count softirqs

Only triggered by irq_exit(), which implies that we called
irq_enter(), which means that we already traced the current
hard IRQ.

1 files changed, 7 insertions, 0 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 154fd689fe02..6440fe53d1a8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1806,7 +1806,14 @@ void scheduler_ipi(void)
         preempt_fold_need_resched();
 
         if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick())
+        {
+#ifndef CONFIG_ARCH_CALLS_IRQ_ENTER_ON_RESCHED_IPI
+                /* If we don't call irq_enter(), we need to triggger the IRQ
+                 * tracing manually. */
+                ft_irq_fired();
+#endif
                 return;
+        }
 
         /*
          * Not all reschedule IPI handlers call irq_enter/irq_exit, since