[CRIU] [PATCH 4/6] pstree: resort code about abandoned tasks

[Andrey Vagin]

From: Andrew Vagin <avagin at virtuozzo.com>

Currently we enumirate all children of the init task and
if a task isn't a session leader, we create a helper,
collect all children with this sid to the children list of this helper.

When all children of the init task has been enumirated, we try to find
a session leader for each helper.

We use this way to enumirate all tasks only once.

Now we are going to collect all tasks in rbtree, so we can find
a sessial leader when we need it. It will not affect performance,
because without searching a session leader, we can't add a helper
to the tree.

Signed-off-by: Andrew Vagin <avagin at virtuozzo.com>
---
 criu/include/pstree.h |  2 --
 criu/pstree.c         | 69 +++++++++++++++++++++------------------------------
 2 files changed, 28 insertions(+), 43 deletions(-)

diff --git a/criu/include/pstree.h b/criu/include/pstree.h
index a742a48..6ff8781 100644
--- a/criu/include/pstree.h
+++ b/criu/include/pstree.h
@@ -64,8 +64,6 @@ static inline bool task_alive(struct pstree_item *i)
 extern void free_pstree(struct pstree_item *root_item);
 extern struct pstree_item *__alloc_pstree_item(bool rst);
 #define alloc_pstree_item() __alloc_pstree_item(false)
-#define alloc_pstree_item_with_rst() __alloc_pstree_item(true)
-extern struct pstree_item *alloc_pstree_helper(void);
 extern void init_pstree_helper(struct pstree_item *ret);
 
 extern struct pstree_item *lookup_create_item(pid_t pid);
diff --git a/criu/pstree.c b/criu/pstree.c
index 8e3c0c9..3274f56 100644
--- a/criu/pstree.c
+++ b/criu/pstree.c
@@ -24,6 +24,8 @@ static struct rb_root pid_root_rb;
 
 #define CLONE_ALLNS     (CLONE_NEWPID | CLONE_NEWNET | CLONE_NEWIPC | CLONE_NEWUTS | CLONE_NEWNS | CLONE_NEWUSER)
 
+#define alloc_pstree_item_with_rst() __alloc_pstree_item(true)
+
 void core_entry_free(CoreEntry *core)
 {
 	if (core->tc && core->tc->timers)
@@ -230,17 +232,6 @@ void init_pstree_helper(struct pstree_item *ret)
 	task_entries->nr_helpers++;
 }
 
-struct pstree_item *alloc_pstree_helper(void)
-{
-	struct pstree_item *ret;
-
-	ret = alloc_pstree_item_with_rst();
-	if (ret)
-		init_pstree_helper(ret);
-
-	return ret;
-}
-
 /* Deep first search on children */
 struct pstree_item *pstree_item_next(struct pstree_item *item)
 {
@@ -586,6 +577,7 @@ static int prepare_pstree_ids(void)
 	 * reparented to init.
 	 */
 	list_for_each_entry(item, &root_item->children, sibling) {
+		struct pstree_item *leader;
 
 		/*
 		 * If a child belongs to the root task's session or it's
@@ -595,15 +587,31 @@ static int prepare_pstree_ids(void)
 		if (item->sid == root_item->sid || item->sid == item->pid.virt)
 			continue;
 
-		helper = alloc_pstree_helper();
-		if (helper == NULL)
-			return -1;
-		helper->sid = item->sid;
-		helper->pgid = item->sid;
-		helper->pid.virt = item->sid;
-		helper->parent = root_item;
-		helper->ids = root_item->ids;
-		list_add_tail(&helper->sibling, &helpers);
+		leader = insert_item(item->sid);
+		if (leader->pid.state != TASK_UNDEF) {
+			helper = insert_item(++max_pid);
+			if (helper == NULL)
+				return -1;
+
+			pr_info("Session leader %d\n", item->sid);
+
+			helper->sid = item->sid;
+			helper->pgid = leader->pgid;
+			helper->ids = leader->ids;
+			helper->parent = leader;
+			list_add(&helper->sibling, &leader->children);
+
+			pr_info("Attach %d to the task %d\n",
+					helper->pid.virt, leader->pid.virt);
+		} else {
+			helper = leader;
+			helper->sid = item->sid;
+			helper->pgid = item->sid;
+			helper->parent = root_item;
+			helper->ids = root_item->ids;
+			list_add_tail(&helper->sibling, &helpers);
+		}
+		init_pstree_helper(helper);
 
 		pr_info("Add a helper %d for restoring SID %d\n",
 				helper->pid.virt, helper->sid);
@@ -663,27 +671,6 @@ static int prepare_pstree_ids(void)
 
 			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, sibling) {
-			if (child->pid.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->sibling, &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 */
-- 
2.5.0