linux-kernel - [PATCH 3/3] add irq tracepoint documentation (take #2)

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Message-Id: <73ff42be3420157667ec548e9b0e409c3cfad05f.1241107197.git.jbaron@redhat.com>
Date:	Thu, 30 Apr 2009 13:29:47 -0400
From:	Jason Baron <jbaron@...hat.com>
To:	mingo@...e.hu
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	rostedt@...dmis.org, fweisbec@...il.com,
	mathieu.desnoyers@...ymtl.ca, randy.dunlap@...cle.com,
	wcohen@...hat.com
Subject: [PATCH 3/3] add irq tracepoint documentation (take #2)


Document irqs for the newly created docbook.

Signed-off-by: Jason Baron <jbaron@...hat.com>
Acked-by: Randy Dunlap <randy.dunlap@...cle.com>

---
 Documentation/DocBook/tracepoint.tmpl |    5 +++
 include/trace/events/irq.h            |   46 ++++++++++++++++++++++++++++++---
 2 files changed, 47 insertions(+), 4 deletions(-)

diff --git a/Documentation/DocBook/tracepoint.tmpl b/Documentation/DocBook/tracepoint.tmpl
index 70891bc..b0756d0 100644
--- a/Documentation/DocBook/tracepoint.tmpl
+++ b/Documentation/DocBook/tracepoint.tmpl
@@ -81,4 +81,9 @@
    </para>
   </chapter>
 
+  <chapter id="irq">
+   <title>IRQ</title>
+!Iinclude/trace/events/irq.h
+  </chapter>
+
 </book>
diff --git a/include/trace/events/irq.h b/include/trace/events/irq.h
index 7686864..32a9f7e 100644
--- a/include/trace/events/irq.h
+++ b/include/trace/events/irq.h
@@ -7,8 +7,16 @@
 #undef TRACE_SYSTEM
 #define TRACE_SYSTEM irq
 
-/*
- * Tracepoint for entry of interrupt handler:
+/**
+ * irq_handler_entry - called immediately before the irq action handler
+ * @irq: irq number
+ * @action: pointer to struct irqaction
+ *
+ * The struct irqaction pointed to by @action contains various
+ * information about the handler, including the device name,
+ * @action->name, and the device id, @action->dev_id. When used in
+ * conjunction with the irq_handler_exit tracepoint, we can figure
+ * out irq handler latencies.
  */
 TRACE_EVENT(irq_handler_entry,
 
@@ -29,8 +37,16 @@ TRACE_EVENT(irq_handler_entry,
 	TP_printk("irq=%d handler=%s", __entry->irq, __get_str(name))
 );
 
-/*
- * Tracepoint for return of an interrupt handler:
+/**
+ * irq_handler_exit - called immediately after the irq action handler returns
+ * @irq: irq number
+ * @action: pointer to struct irqaction
+ * @ret: return value
+ *
+ * If the @ret value is set to IRQ_HANDLED, then we know that the corresponding
+ * @action->handler scuccessully handled this irq. Otherwise, the irq might be
+ * a shared irq line, or the irq was not handled successfully. Can be used in
+ * conjunction with the irq_handler_entry to understand irq handler latencies.
  */
 TRACE_EVENT(irq_handler_exit,
 
@@ -52,6 +68,17 @@ TRACE_EVENT(irq_handler_exit,
 		  __entry->irq, __entry->ret ? "handled" : "unhandled")
 );
 
+/**
+ * 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
+ *
+ * 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
+ * we can determine the softirq latency.
+ */
 TRACE_EVENT(softirq_entry,
 
 	TP_PROTO(struct softirq_action *h, struct softirq_action *vec),
@@ -71,6 +98,17 @@ TRACE_EVENT(softirq_entry,
 	TP_printk("softirq=%d action=%s", __entry->vec, __get_str(name))
 );
 
+/**
+ * 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
+ *
+ * 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.
+ */
 TRACE_EVENT(softirq_exit,
 
 	TP_PROTO(struct softirq_action *h, struct softirq_action *vec),
-- 
1.6.0.6

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