[CRIU] [PATCH 5/5] pstree: use rbtree to find a specified pid

[Pavel Emelyanov]

On 02/19/2016 09:13 PM, Andrey Vagin wrote:
> From: Andrew Vagin <avagin at virtuozzo.com>
> 
> Signed-off-by: Andrew Vagin <avagin at virtuozzo.com>
> ---
>  criu/pstree.c | 36 +++++++++++++++++++++++++-----------
>  1 file changed, 25 insertions(+), 11 deletions(-)
> 
> diff --git a/criu/pstree.c b/criu/pstree.c
> index 61fd5d3..f82a3de 100644
> --- a/criu/pstree.c
> +++ b/criu/pstree.c
> @@ -383,6 +383,23 @@ static int prepare_pstree_for_shell_job(void)
>  	return 0;
>  }
>  
> +static struct pid *lookup_pid(pid_t pid)

We already have pstree_item_by_virt and pstree_item_by_real. Why do we need one more?

> +{
> +	struct rb_node *node = root_rb.rb_node;
> +
> +	while (node) {
> +		struct pid *this = rb_entry(node, struct pid, node);
> +
> +		if (pid < this->virt)
> +			node = node->rb_left;
> +		else if (pid > this->virt)
> +			node = node->rb_right;
> +		else
> +			return this;
> +	}
> +	return NULL;
> +}
> +
>  static struct pid *insert_pid(pid_t pid, struct pid *pid_node)
>  {
>  	struct rb_node *node = root_rb.rb_node;
> @@ -686,18 +703,15 @@ static int prepare_pstree_ids(void)
>  
>  	/* Add a process group leader if it is absent  */
>  	for_each_pstree_item(item) {
> -		struct pstree_item *gleader;
> +		struct pid *pid;
>  
>  		if (!item->pgid || item->pid.virt == item->pgid)
>  			continue;
>  
> -		for_each_pstree_item(gleader) {
> -			if (gleader->pid.virt == item->pgid)
> -				break;
> -		}
> -
> -		if (gleader) {
> -			rsti(item)->pgrp_leader = gleader;
> +		pid = lookup_pid(item->pgid);
> +		if (pid->state != TASK_UNDEF) {
> +			BUG_ON(pid->state == TASK_THREAD);
> +			rsti(item)->pgrp_leader = container_of(pid, struct pstree_item, pid);
>  			continue;
>  		}
>  
> @@ -709,9 +723,9 @@ static int prepare_pstree_ids(void)
>  		if (current_pgid == item->pgid)
>  			continue;
>  
> -		helper = alloc_pstree_helper();
> -		if (helper == NULL)
> -			return -1;
> +		helper = container_of(pid, struct pstree_item, pid);
> +		init_pstree_helper(helper);
> +
>  		helper->sid = item->sid;
>  		helper->pgid = item->pgid;
>  		helper->pid.virt = item->pgid;
>