[PATCH 0/3] ftrace: add tracepoint for timer event

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

Hi,

We can know timer's whole lifecycle as init/start/expire/cancel by
these tracepoints. 

Following tracepoints are introduced as ingo's suggestion in
	http://marc.info/?l=linux-kernel&m=123791899529128&w=2

for timer:
trace_timer_init()
trace_timer_start()
trace_timer_expire()
trace_timer_cancel()

for hrtimer:
trace_hrtimer_init()
trace_hrtimer_start()
trace_hrtimer_expire()
trace_hrtimer_cancel()

for itimer:
itimer_start()
itimer_expire()
itimer_cancel()

Example ftrace output:
for timer:
           <...>-2998  [000] 63501.542376: timer_init: timer=e0b374e0
           <...>-2998  [000] 63501.542424: timer_start: timer=e0b374e0 func=test_timerfuc expires=4294941565 cpu=0
	  <idle>-0     [000] 63514.508219: timer_expire: timer=e0b374e0 func=test_timerfuc
          <idle>-0     [000] 63514.508222: timer_cancel: timer=e0b374e0 func=test_timerfuc

for hrtimer:
           <...>-3628  [001] 64228.304772: hrtimer_init: timer=e0b404cc clockid=CLOCK_REALTIME mode=HRTIMER_MODE_ABS
           <...>-3628  [001] 64228.304793: hrtimer_start: timer=e0b404cc func=test_hrtime expires=1242920654000000000 ns softexpires=1242920654000000000 ns
     ksoftirqd/1-7     [001] 64228.304858: hrtimer_expire: timer=e0b404cc func=test_hrtime
     ksoftirqd/1-7     [001] 64228.304860: hrtimer_cancel: timer=e0b404cc func=test_hrtime

for itimer:
           <...>-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

We already have debugobject in timer to init/activate/deactivate/free,
but it can't be covered function of there tracepoints, because:
1: We can't get timer's lifecycle information in userspace by debugobject,
   it is necessary for system engineer to investigate system trouble caused
   by using timer.
2: We can't get information of whole lifecycle of timer by debugobject, 
   for example, deactivation of a timer.
3: There are many different tracing code in many kernel subsystem as blktrace,
   debugobject, and tracepoint is designed as generic way to unify these
   tracing way.

include/trace/events/timer.h |  249 +++++++++++++++++++++++++++++++++++++++++++
 kernel/hrtimer.c             |    5
 kernel/itimer.c              |   17 ++
 kernel/posix-cpu-timers.c    |    3
 kernel/timer.c               |    9 +
 5 files changed, 279 insertions(+), 4 deletions(-)