[CRIU] Re: [PATCH cr 5/6] pstree: allocate rst parts from a shared region

[Pavel Emelyanov]

On 10/02/2012 06:07 PM, Andrey Vagin wrote:
> The next patch will add a futex, which will be used for restoring
> shared fd tables.
> 
> Signed-off-by: Andrey Vagin <avagin at openvz.org>
> ---
>  include/pstree.h |    2 +-
>  pstree.c         |    8 +++++++-
>  2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/include/pstree.h b/include/pstree.h
> index 0790b49..2da7176 100644
> --- a/include/pstree.h
> +++ b/include/pstree.h
> @@ -20,7 +20,7 @@ struct pstree_item {
>  	int			state;		/* TASK_XXX constants */
>  	int			nr_threads;	/* number of threads */
>  	struct pid		*threads;	/* array of threads */
> -	struct rst_info		rst[0];
> +	struct rst_info		*rst;
>  };
>  
>  extern void free_pstree(struct pstree_item *root_item);
> diff --git a/pstree.c b/pstree.c
> index 8df5a63..1672b26 100644
> --- a/pstree.c
> +++ b/pstree.c
> @@ -33,10 +33,16 @@ struct pstree_item *__alloc_pstree_item(bool rst)
>  {
>  	struct pstree_item *item;
>  
> -	item = xzalloc(sizeof(*item) + (rst ? sizeof(item->rst[0]) : 0));
> +	item = xzalloc(sizeof(*item));
>  	if (!item)
>  		return NULL;
>  
> +	if (rst) {
> +		item->rst = shmalloc(sizeof(item->rst[0]));

The smalloc has caveat -- it's hared with children _only_. Does that suit us?
Thing #2. The rst_info is generic rst_info, what if we add there something which
is not fdtable related? Things will get broken.

> +		if (!item->rst)
> +			return NULL;
> +	}
> +
>  	INIT_LIST_HEAD(&item->children);
>  	item->threads = NULL;
>  	item->nr_threads = 0;
>