linux-kernel - Re: how to find a task through name faster?

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Date:	Mon, 11 Jul 2011 11:23:44 -0700
From:	Muthu Kumar <muthu.lkml@...il.com>
To:	loody <miloody@...il.com>
Cc:	Chris Friesen <chris.friesen@...band.com>,
	linux-kernel@...r.kernel.org
Subject: Re: how to find a task through name faster?

Let me ask a trivial question: Should this be done in kernel? Can't
you push it to user space and walk the /proc to find if the process is
there.

On Mon, Jul 11, 2011 at 10:57 AM, loody <miloody@...il.com> wrote:
> hi:
>
> 2011/7/12 Chris Friesen <chris.friesen@...band.com>:
>> On 07/11/2011 10:52 AM, loody wrote:
>>>
>>> hi all:
>>> I found a way to find a task I need by name, test,  as below:
>>> for_each_process(task) {
>>>     if(strcmp(task->comm, "test")
>>>         printk(“%s[%d]\n”, task->comm, task->pid);
>>> }
>>>
>>> But it is time-consuming to do so if I periodically want to know
>>> whether "test" exist or not.
>>> is there better way to do so?
>
> Thanks for your reply
>
>> The names of tasks isn't indexed in any way so the above is about as good as
>> it gets if that's all the information you have.
>
> actually, I only have the name for searching, since the thread start
>  and finish periodically, pid of it will change dynamically. If I save
> the pid, next time it will change and be no use to me
>>
>> One common way around that is to store the PID in a file somewhere at
>> startup.  Then you can look in the file and see if that PID is present and
>> check "task->comm" to make sure it's what you expect.  This saves having to
>> search through all tasks.
>>
>> Chris
>
>
> --
> Regards,
> --
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