[PATCH 3/3] ftrace: add tracepoint for itimer

[Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>]

This patch can trace itimer start/expire/cancle event

Example ftrace output:
           <...>-4183  [001] 66533.730163: itimer_start: task=main which=0 it_value=13000000000 it_interval=0
          <idle>-0     [001] 66546.698154: itimer_expire: task=main which=0
           <...>-4183  [000] 66546.698533: itimer_cancel: task=main which=0

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
---
 include/trace/events/timer.h |   66 ++++++++++++++++++++++++++++++++++++++++++
 kernel/itimer.c              |   17 +++++++++--
 kernel/posix-cpu-timers.c    |    3 ++
 3 files changed, 83 insertions(+), 3 deletions(-)

diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index e5dc9d5..767c703 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -175,6 +175,72 @@ TRACE_EVENT(hrtimer_cancel,
 	TP_printk("timer=%p func=%pf", __entry->timer, __entry->function)
 );
 
+TRACE_EVENT(itimer_start,
+
+	TP_PROTO(int which, struct itimerval *value),
+
+	TP_ARGS(which, value),
+
+	TP_STRUCT__entry(
+		__field(	int,			which		)
+		__field(	unsigned long long,	it_value	)
+		__field(	unsigned long long,	it_interval	)
+		__string(	comm,   		current->comm   )
+	),
+
+	TP_fast_assign(
+		__entry->which		= which;
+		__entry->it_value	= (which == ITIMER_REAL ?
+			ktime_to_ns(timeval_to_ktime(value->it_value)) :
+			timeval_to_cputime(&value->it_value));
+		 __entry->it_interval 	= (which == ITIMER_REAL ?
+			ktime_to_ns(timeval_to_ktime(value->it_interval)) :
+			timeval_to_cputime(&value->it_interval));
+		__assign_str(comm, current->comm);
+	),
+
+	TP_printk("task=%s which=%d it_value=%llu it_interval=%llu", __get_str(comm),
+		  __entry->which, __entry->it_value, __entry->it_interval)
+);
+
+TRACE_EVENT(itimer_expire,
+
+	TP_PROTO(int which, struct task_struct *task),
+
+	TP_ARGS(which, task),
+
+	TP_STRUCT__entry(
+		__field(  int ,	which		)
+		__string( comm,	task->comm	)
+	),
+
+	TP_fast_assign(
+		__entry->which	 = which;
+		__assign_str(comm, task->comm);
+	),
+
+	TP_printk("task=%s which=%d", __get_str(comm), __entry->which)
+);
+
+TRACE_EVENT(itimer_cancel,
+
+	TP_PROTO(int which),
+
+	TP_ARGS(which),
+
+	TP_STRUCT__entry(
+		__field(  int ,	which		)
+		__string( comm, current->comm	)
+	),
+
+	TP_fast_assign(
+		__entry->which	= which;
+		__assign_str(comm, current->comm);
+	),
+
+	TP_printk("task=%s which=%d", __get_str(comm), __entry->which)
+);
+
 #endif /*  _TRACE_TIMER_H */
 
 /* This part must be outside protection */
diff --git a/kernel/itimer.c b/kernel/itimer.c
index 58762f7..1d2dd64 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -12,6 +12,7 @@
 #include <linux/time.h>
 #include <linux/posix-timers.h>
 #include <linux/hrtimer.h>
+#include <trace/events/timer.h>
 
 #include <asm/uaccess.h>
 
@@ -123,6 +124,7 @@ enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 	struct signal_struct *sig =
 		container_of(timer, struct signal_struct, real_timer);
 
+	trace_itimer_expire(ITIMER_REAL, pid_task(sig->leader_pid, PIDTYPE_PID));
 	kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
 
 	return HRTIMER_NORESTART;
@@ -168,8 +170,11 @@ again:
 			tsk->signal->it_real_incr =
 				timeval_to_ktime(value->it_interval);
 			hrtimer_start(timer, expires, HRTIMER_MODE_REL);
-		} else
+			trace_itimer_start(ITIMER_REAL, value);
+		} else{
 			tsk->signal->it_real_incr.tv64 = 0;
+			trace_itimer_cancel(ITIMER_REAL);
+		}
 
 		spin_unlock_irq(&tsk->sighand->siglock);
 		break;
@@ -186,7 +191,10 @@ again:
 						   jiffies_to_cputime(1));
 			set_process_cpu_timer(tsk, CPUCLOCK_VIRT,
 					      &nval, &cval);
-		}
+			trace_itimer_start(ITIMER_VIRTUAL, value);
+		}else
+			trace_itimer_cancel(ITIMER_VIRTUAL);
+
 		tsk->signal->it_virt_expires = nval;
 		tsk->signal->it_virt_incr = ninterval;
 		spin_unlock_irq(&tsk->sighand->siglock);
@@ -208,7 +216,10 @@ again:
 						   jiffies_to_cputime(1));
 			set_process_cpu_timer(tsk, CPUCLOCK_PROF,
 					      &nval, &cval);
-		}
+			trace_itimer_start(ITIMER_PROF, value);
+		}else
+			trace_itimer_cancel(ITIMER_PROF);
+
 		tsk->signal->it_prof_expires = nval;
 		tsk->signal->it_prof_incr = ninterval;
 		spin_unlock_irq(&tsk->sighand->siglock);
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index bece7c0..edb4e8c 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -8,6 +8,7 @@
 #include <linux/math64.h>
 #include <asm/uaccess.h>
 #include <linux/kernel_stat.h>
+#include <trace/events/timer.h>
 
 /*
  * Called after updating RLIMIT_CPU to set timer expiration if necessary.
@@ -1160,6 +1161,7 @@ static void check_process_timers(struct task_struct *tsk,
 				sig->it_prof_expires = cputime_add(
 					sig->it_prof_expires, ptime);
 			}
+			trace_itimer_expire(ITIMER_PROF, tsk);
 			__group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
 		}
 		if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
@@ -1176,6 +1178,7 @@ static void check_process_timers(struct task_struct *tsk,
 				sig->it_virt_expires = cputime_add(
 					sig->it_virt_expires, utime);
 			}
+			trace_itimer_expire(ITIMER_VIRTUAL, tsk);
 			__group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
 		}
 		if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
-- 
1.6.1.2