tracing: tracepoints for softirq entry/exit - tracepoints

Introduce softirq entry/exit tracepoints. These are useful for
augmenting existing tracers, and to figure out softirq frequencies and
timings.

[
  s/irq_softirq_/softirq_/ for trace point names and
  Fixed printf format in TRACE_FORMAT macro
   - Steven Rostedt
]

LKML-Reference: <20090312183603.GC3352@redhat.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>

2 files changed, 18 insertions, 1 deletions

diff --git a/include/trace/irq_event_types.h b/include/trace/irq_event_types.h
index 214bb928fe9e..85964ebd47ec 100644
--- a/include/trace/irq_event_types.h
+++ b/include/trace/irq_event_types.h
@@ -40,4 +40,16 @@ TRACE_EVENT(irq_handler_exit,
                   __entry->irq, __entry->ret ? "handled" : "unhandled")
 );
 
+TRACE_FORMAT(softirq_entry,
+        TP_PROTO(struct softirq_action *h, struct softirq_action *vec),
+        TP_ARGS(h, vec),
+        TP_FMT("softirq=%d action=%s", (int)(h - vec), softirq_to_name[h-vec])
+        );
+
+TRACE_FORMAT(softirq_exit,
+        TP_PROTO(struct softirq_action *h, struct softirq_action *vec),
+        TP_ARGS(h, vec),
+        TP_FMT("softirq=%d action=%s", (int)(h - vec), softirq_to_name[h-vec])
+        );
+
 #undef TRACE_SYSTEM
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 9f90fdc039f4..a5e81231ca7a 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -24,6 +24,7 @@
 #include <linux/ftrace.h>
 #include <linux/smp.h>
 #include <linux/tick.h>
+#include <trace/irq.h>
 
 #include <asm/irq.h>
 /*
@@ -186,6 +187,9 @@ EXPORT_SYMBOL(local_bh_enable_ip);
  */
 #define MAX_SOFTIRQ_RESTART 10
 
+DEFINE_TRACE(softirq_entry);
+DEFINE_TRACE(softirq_exit);
+
 asmlinkage void __do_softirq(void)
 {
         struct softirq_action *h;
@@ -212,8 +216,9 @@ restart:
                 if (pending & 1) {
                         int prev_count = preempt_count();
 
+                        trace_softirq_entry(h, softirq_vec);
                         h->action(h);
-
+                        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,"