[RFC PATCH v3 1/5] irq: add tracepoint to softirq_raise

[Koki Sanagi <sanagi.koki@jp.fujitsu.com>]

From: Lai Jiangshan <laijs@cn.fujitsu.com>

Add a tracepoint for tracing when softirq action is raised.

It and the existed tracepoints complete softirq's tracepoints:
softirq_raise, softirq_entry and softirq_exit.

And when this tracepoint is used in combination with
the softirq_entry tracepoint we can determine
the softirq raise latency.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>

[ factorize softirq events with DECLARE_EVENT_CLASS ]
Signed-off-by: Koki Sanagi <sanagi.koki@jp.fujitsu.com>
---
 include/linux/interrupt.h  |    8 +++++-
 include/trace/events/irq.h |   57 ++++++++++++++++++++++++++-----------------
 kernel/softirq.c           |    4 +-
 3 files changed, 43 insertions(+), 26 deletions(-)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index c233113..1cb5726 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -18,6 +18,7 @@
 #include <asm/atomic.h>
 #include <asm/ptrace.h>
 #include <asm/system.h>
+#include <trace/events/irq.h>
 
 /*
  * These correspond to the IORESOURCE_IRQ_* defines in
@@ -402,7 +403,12 @@ asmlinkage void do_softirq(void);
 asmlinkage void __do_softirq(void);
 extern void open_softirq(int nr, void (*action)(struct softirq_action *));
 extern void softirq_init(void);
-#define __raise_softirq_irqoff(nr) do { or_softirq_pending(1UL << (nr)); } while (0)
+static inline void __raise_softirq_irqoff(unsigned int nr)
+{
+	trace_softirq_raise(nr);
+	or_softirq_pending(1UL << nr);
+}
+
 extern void raise_softirq_irqoff(unsigned int nr);
 extern void raise_softirq(unsigned int nr);
 extern void wakeup_softirqd(void);
diff --git a/include/trace/events/irq.h b/include/trace/events/irq.h
index 0e4cfb6..717744c 100644
--- a/include/trace/events/irq.h
+++ b/include/trace/events/irq.h
@@ -5,7 +5,9 @@
 #define _TRACE_IRQ_H
 
 #include <linux/tracepoint.h>
-#include <linux/interrupt.h>
+
+struct irqaction;
+struct softirq_action;
 
 #define softirq_name(sirq) { sirq##_SOFTIRQ, #sirq }
 #define show_softirq_name(val)				\
@@ -84,56 +86,65 @@ TRACE_EVENT(irq_handler_exit,
 
 DECLARE_EVENT_CLASS(softirq,
 
-	TP_PROTO(struct softirq_action *h, struct softirq_action *vec),
+	TP_PROTO(unsigned int nr),
 
-	TP_ARGS(h, vec),
+	TP_ARGS(nr),
 
 	TP_STRUCT__entry(
-		__field(	int,	vec			)
+		__field(	unsigned int,	vec	)
 	),
 
 	TP_fast_assign(
-		__entry->vec = (int)(h - vec);
+		__entry->vec	= nr;
 	),
 
 	TP_printk("vec=%d [action=%s]", __entry->vec,
-		  show_softirq_name(__entry->vec))
+		show_softirq_name(__entry->vec))
+);
+
+/**
+ * softirq_raise - called immediately when a softirq is raised
+ * @nr: softirq vector number
+ *
+ * Tracepoint for tracing when softirq action is raised.
+ * Also, when used in combination with the softirq_entry tracepoint
+ * we can determine the softirq raise latency.
+ */
+DEFINE_EVENT(softirq, softirq_raise,
+
+	TP_PROTO(unsigned int nr),
+
+	TP_ARGS(nr)
 );
 
 /**
  * softirq_entry - called immediately before the softirq handler
- * @h: pointer to struct softirq_action
- * @vec: pointer to first struct softirq_action in softirq_vec array
+ * @nr: softirq vector number
  *
- * The @h parameter, contains a pointer to the struct softirq_action
- * which has a pointer to the action handler that is called. By subtracting
- * the @vec pointer from the @h pointer, we can determine the softirq
- * number. Also, when used in combination with the softirq_exit tracepoint
+ * Tracepoint for tracing when softirq action starts.
+ * Also, when used in combination with the softirq_exit tracepoint
  * we can determine the softirq latency.
  */
 DEFINE_EVENT(softirq, softirq_entry,
 
-	TP_PROTO(struct softirq_action *h, struct softirq_action *vec),
+	TP_PROTO(unsigned int nr),
 
-	TP_ARGS(h, vec)
+	TP_ARGS(nr)
 );
 
 /**
  * softirq_exit - called immediately after the softirq handler returns
- * @h: pointer to struct softirq_action
- * @vec: pointer to first struct softirq_action in softirq_vec array
+ * @nr: softirq vector number
  *
- * The @h parameter contains a pointer to the struct softirq_action
- * that has handled the softirq. By subtracting the @vec pointer from
- * the @h pointer, we can determine the softirq number. Also, when used in
- * combination with the softirq_entry tracepoint we can determine the softirq
- * latency.
+ * Tracepoint for tracing when softirq action ends.
+ * Also, when used in combination with the softirq_entry tracepoint
+ * we can determine the softirq latency.
  */
 DEFINE_EVENT(softirq, softirq_exit,
 
-	TP_PROTO(struct softirq_action *h, struct softirq_action *vec),
+	TP_PROTO(unsigned int nr),
 
-	TP_ARGS(h, vec)
+	TP_ARGS(nr)
 );
 
 #endif /*  _TRACE_IRQ_H */
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 825e112..6790599 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -215,9 +215,9 @@ restart:
 			int prev_count = preempt_count();
 			kstat_incr_softirqs_this_cpu(h - softirq_vec);
 
-			trace_softirq_entry(h, softirq_vec);
+			trace_softirq_entry(h - softirq_vec);
 			h->action(h);
-			trace_softirq_exit(h, softirq_vec);
+			trace_softirq_exit(h - softirq_vec);
 			if (unlikely(prev_count != preempt_count())) {
 				printk(KERN_ERR "huh, entered softirq %td %s %p"
 				       "with preempt_count %08x,"