Re: [LTP] [PATCH] Fix disable set_ftrace_pid in ftrace_set_ftrace_pid.sh

[Li Zefan <lizf@cn.fujitsu.com>]

于 2011年02月22日 09:58, Han Pingtian 写道:
> On Mon, Feb 21, 2011 at 03:44:11PM +0800, Li Zefan wrote:
>> Han Pingtian wrote:
>>> It seems we need echo -1 to set_ftrace_pid to disable in. Or we'll get
>>> these error message when running ftrace_stress:
>>>
>>
>> kernel version?
> 2.6.32-114.0.1.el6.x86_64 , RHEL6.1.
>>
>> This is the result from latest kernel:
>>
>> # echo > set_ftrace_pid
>> # echo -1 > set_ftrace_pid
>> bash: echo: write error: Invalid argument
>>
> Looks like latest kernel changed the behaviour. But the

The change came from commit 756d17ee7ee4fbc8238bdf97100af63e6ac441ef

So we have to check the kernel version, or try both "echo > ..." and
"echo -1 > ...".

> Documentation/trace/ftrace.txt hasn't been updated:
> 
>      yum-updatesd-3111  [003]  1637.254683: lock_hrtimer_base <-hrtimer_try_to_cancel
>      yum-updatesd-3111  [003]  1637.254685: fget_light <-do_sys_poll
>      yum-updatesd-3111  [003]  1637.254686: pipe_poll <-do_sys_poll
> # echo -1 > set_ftrace_pid
> # cat trace |head
>  # tracer: function
>  #
>  #           TASK-PID    CPU#    TIMESTAMP  FUNCTION

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