Re: [PATCH 5/20] Introduce struct upid

[sukadev@us.ibm.com]

Andrew Morton [akpm@linux-foundation.org] wrote:
| On Fri, 10 Aug 2007 15:47:59 +0400
| xemul@openvz.org wrote:
| 
| >  struct pid
| >  {
| >  	atomic_t count;
| > @@ -50,6 +50,8 @@ struct pid
| >  	/* lists of tasks that use this pid */
| >  	struct hlist_head tasks[PIDTYPE_MAX];
| >  	struct rcu_head rcu;
| > +	int level;
| > +	struct upid numbers[1];
| 
| You can make this have size [0] now.  It's a gcc extension and
| is used elsewhere in the kernel.

Sorry, we did not respond to this yet :-)

Well, every process has at least one 'struct upid'. The only "cost"
I see with size [1] is having to subtract 1 in create_pid_cachep().

Besides, we create/initialize the 'struct pid' for the idle process
by hand (see INIT_STRUCT_PID in init_task.h).

If we set this size to [0] now, we would need to dynamically allocate
a 'struct upid' during early boot and attach this upid to init_struct_pid.

Or is there a easy way to attach a 'upid' to init_struct_pid, statically ?

Suka