itimers: Add tracepoints for itimer

Add tracepoints for all itimer variants: ITIMER_REAL, ITIMER_VIRTUAL
and ITIMER_PROF.

[ tglx: Fixed comments and made the output more readable, parseable
  	and consistent. Replaced pid_vnr by pid_nr because the hrtimer
  	callback can happen in any namespace ]

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Anton Blanchard <anton@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Zhaolei <zhaolei@cn.fujitsu.com>
LKML-Reference: <4A7F8B6E.2010109@cn.fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

3 files changed, 77 insertions, 1 deletions

diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index df3c07fa0cb8..1844c48d640e 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -270,6 +270,72 @@ TRACE_EVENT(hrtimer_cancel,
         TP_printk("hrtimer %p", __entry->timer)
 );
 
+/**
+ * itimer_state - called when itimer is started or canceled
+ * @which:      name of the interval timer
+ * @value:      the itimers value, itimer is canceled if value->it_value is
+ *              zero, otherwise it is started
+ * @expires:    the itimers expiry time
+ */
+TRACE_EVENT(itimer_state,
+
+        TP_PROTO(int which, const struct itimerval *const value,
+                 cputime_t expires),
+
+        TP_ARGS(which, value, expires),
+
+        TP_STRUCT__entry(
+                __field(        int,            which           )
+                __field(        cputime_t,      expires         )
+                __field(        long,           value_sec       )
+                __field(        long,           value_usec      )
+                __field(        long,           interval_sec    )
+                __field(        long,           interval_usec   )
+        ),
+
+        TP_fast_assign(
+                __entry->which          = which;
+                __entry->expires        = expires;
+                __entry->value_sec      = value->it_value.tv_sec;
+                __entry->value_usec     = value->it_value.tv_usec;
+                __entry->interval_sec   = value->it_interval.tv_sec;
+                __entry->interval_usec  = value->it_interval.tv_usec;
+        ),
+
+        TP_printk("which %d, expires %lu, it_value %lu.%lu, it_interval %lu.%lu",
+                  __entry->which, __entry->expires,
+                  __entry->value_sec, __entry->value_usec,
+                  __entry->interval_sec, __entry->interval_usec)
+);
+
+/**
+ * itimer_expire - called when itimer expires
+ * @which:      type of the interval timer
+ * @pid:        pid of the process which owns the timer
+ * @now:        current time, used to calculate the latency of itimer
+ */
+TRACE_EVENT(itimer_expire,
+
+        TP_PROTO(int which, struct pid *pid, cputime_t now),
+
+        TP_ARGS(which, pid, now),
+
+        TP_STRUCT__entry(
+                __field( int ,          which   )
+                __field( pid_t,         pid     )
+                __field( cputime_t,     now     )
+        ),
+
+        TP_fast_assign(
+                __entry->which  = which;
+                __entry->now    = now;
+                __entry->pid    = pid_nr(pid);
+        ),
+
+            TP_printk("which %d, pid %d, now %lu", __entry->which,
+                      (int) __entry->pid, __entry->now)
+);
+
 #endif /*  _TRACE_TIMER_H */
 
 /* This part must be outside protection */
diff --git a/kernel/itimer.c b/kernel/itimer.c
index 8078a32d3b10..b03451ede528 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>
 
@@ -122,6 +123,7 @@ 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, sig->leader_pid, 0);
         kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
 
         return HRTIMER_NORESTART;
@@ -166,6 +168,8 @@ static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
         }
         it->expires = nval;
         it->incr = ninterval;
+        trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
+                           ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
 
         spin_unlock_irq(&tsk->sighand->siglock);
 
@@ -217,6 +221,7 @@ again:
                 } else
                         tsk->signal->it_real_incr.tv64 = 0;
 
+                trace_itimer_state(ITIMER_REAL, value, 0);
                 spin_unlock_irq(&tsk->sighand->siglock);
                 break;
         case ITIMER_VIRTUAL:
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 12161f74744e..5c9dc228747b 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.
@@ -1090,9 +1091,13 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
                                                           cputime_one_jiffy);
                                 it->error -= onecputick;
                         }
-                } else
+                } else {
                         it->expires = cputime_zero;
+                }
 
+                trace_itimer_expire(signo == SIGPROF ?
+                                    ITIMER_PROF : ITIMER_VIRTUAL,
+                                    tsk->signal->leader_pid, cur_time);
                 __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
         }