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restore: restore sids of tasks, which have been reparented to init (v3)

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* Create helpers for processes which have been reparented to init.
* Insert helpers in a process tree.
* Helpers will exit after constructing a process tree.

v2: fix variables names and check errors
v3: add comments in code

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
This commit is contained in:
Andrey Vagin 2012-06-22 00:39:00 +04:00 committed by Pavel Emelyanov
parent eb9a6f2015
commit 2c412fa6ac
1 changed files with 87 additions and 0 deletions
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87
cr-restore.c
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@ -172,6 +172,90 @@ static int prepare_pstree(void)
return ret;
}
static int prepare_pstree_ids(void)
{
struct pstree_item *item, *child, *helper, *tmp;
LIST_HEAD(helpers);
/*
* Some task can be reparented to init. A helper task should be added
* for restoring sid of such tasks. The helper tasks will be exited
* immediately after forking children and all children will be
* reparented to init.
*/
list_for_each_entry(item, &root_item->children, list) {
if (item->sid == root_item->sid || item->sid == item->pid.virt)
continue;
helper = alloc_pstree_item();
if (helper == NULL)
return -1;
helper->sid = item->sid;
helper->pgid = item->sid;
helper->pid.virt = item->sid;
helper->state = TASK_HELPER;
helper->parent = root_item;
list_add_tail(&helper->list, &helpers);
pr_info("Add a helper %d for restoring SID %d\n",
helper->pid.virt, helper->sid);
child = list_entry(item->list.prev, struct pstree_item, list);
item = child;
list_for_each_entry_safe_continue(child, tmp, &root_item->children, list) {
if (child->sid != helper->sid)
continue;
if (child->sid == child->pid.virt)
continue;
pr_info("Attach %d to the temporary task %d\n",
child->pid.virt, helper->pid.virt);
child->parent = helper;
list_move(&child->list, &helper->children);
}
}
/* Try to connect helpers to session leaders */
for_each_pstree_item(item) {
if (!item->parent) /* skip the root task */
continue;
if (item->state == TASK_HELPER)
continue;
if (item->sid != item->pid.virt)
continue;
pr_info("Session leader %d\n", item->sid);
/* Try to find helpers, who should be connected to the leader */
list_for_each_entry(child, &helpers, list) {
if (child->state != TASK_HELPER)
continue;
if (child->sid != item->sid)
continue;
child->pgid = item->pgid;
child->pid.virt = ++max_pid;
child->parent = item;
list_move(&child->list, &item->children);
pr_info("Attach %d to the task %d\n",
child->pid.virt, item->pid.virt);
break;
}
}
/* All other helpers are session leaders for own sessions */
list_splice(&helpers, &root_item->children);
return 0;
}
static int prepare_shared(void)
{
int ret = 0;
@ -885,6 +969,9 @@ static int restore_all_tasks(pid_t pid, struct cr_options *opts)
if (prepare_shared() < 0)
return -1;
if (prepare_pstree_ids() < 0)
return -1;
return restore_root_task(root_item, opts);
}