Re: What's the relationship between pid and pid_t

[Aiolia Lea <casmyu@xxxxxxxxx>]

Hi,

Thanks for your reply.

But I still confuse about the usage.

Is anybody could give me some more detailed information?

Thank you very much~

On Tue, Jul 20, 2010 at 11:24 AM, Tushar Dadlani <tush726@xxxxxxxxx> wrote:

Hi,

struct pid is a drop in replacement for a 
pid_t (except for the need for reference counting. 

Found this here http://lwn.net/Articles/257054/

On Tue, Jul 20, 2010 at 8:26 AM, Aiolia Lea <casmyu@xxxxxxxxx> wrote:

Hi, All

From linux kernel (2.6.30.4), I found two data structures, as follow:

typedef __kernel_pid_t        pid_t;

struct pid
{
    atomic_t count;
    unsigned int level;
    /* lists of tasks that use this pid */
    struct hlist_head tasks[PIDTYPE_MAX];
    struct rcu_head rcu;
    struct upid numbers[1];
};

According to my understanding, the pid_t is the frequent item we know, such as in getpid() function, ps command and also.

Then, what's the pid structure used for? and what's the relationship between pid structure and pid_t?

Why the kernel required to involved pid this structure?

Hope you could give me some explanation or some  links.

Thank you very much~
--
Best Regards!
Aiolia Lea

--
Tushar Dadlani
Manipal Institute of Technology
+919986292434

-- 
Best Regards!
Aiolia Lea