Feather-Trace: keep track of interrupt-related interference.2012.1

Increment a processor-local counter whenever an interrupt is handled.
This allows Feather-Trace to include a (truncated) counter and a flag
to report interference from interrupts. This could be used to filter
samples that were disturbed by interrupts.

3 files changed, 28 insertions, 1 deletions

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index ba362171e8ae..e6dd5a456bae 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -6,6 +6,8 @@
 #include <linux/ftrace_irq.h>
 #include <asm/hardirq.h>
 
+#include <litmus/trace_irq.h>
+
 /*
  * We put the hardirq and softirq counter into the preemption
  * counter. The bitmask has the following meaning:
@@ -186,6 +188,7 @@ extern void rcu_nmi_exit(void);
                 account_system_vtime(current);          \
                 add_preempt_count(HARDIRQ_OFFSET);      \
                 trace_hardirq_enter();                  \
+                ft_irq_fired();                         \
         } while (0)
 
 /*
@@ -216,6 +219,7 @@ extern void irq_exit(void);
                 lockdep_off();                                  \
                 rcu_nmi_enter();                                \
                 trace_hardirq_enter();                          \
+                ft_irq_fired();                                 \
         } while (0)
 
 #define nmi_exit()                                              \
diff --git a/include/litmus/trace.h b/include/litmus/trace.h
index e2926a08c2f4..e809376d6487 100644
--- a/include/litmus/trace.h
+++ b/include/litmus/trace.h
@@ -20,7 +20,9 @@ struct timestamp {
         uint32_t                seq_no;
         uint8_t                 cpu;
         uint8_t                 event;
-        uint8_t                 task_type;
+        uint8_t                 task_type:2;
+        uint8_t                 irq_flag:1;
+        uint8_t                 irq_count:5;
 };
 
 /* tracing callbacks */
diff --git a/include/litmus/trace_irq.h b/include/litmus/trace_irq.h
new file mode 100644
index 000000000000..f18b127a089d
--- /dev/null
+++ b/include/litmus/trace_irq.h
@@ -0,0 +1,21 @@
+#ifndef _LITMUS_TRACE_IRQ_H_
+#define _LITMUS_TRACE_IRQ_H_
+
+#ifdef CONFIG_SCHED_OVERHEAD_TRACE
+
+extern DEFINE_PER_CPU(atomic_t, irq_fired_count);
+
+static inline void ft_irq_fired(void)
+{
+        /* Only called with preemptions disabled.  */
+        atomic_inc(&__get_cpu_var(irq_fired_count));
+}
+
+
+#else
+
+#define ft_irq_fired() /* nothing to do */
+
+#endif
+
+#endif