restore: wait while restroring pgid (v2)

Pgid leader should become such before any other task tries
to enter this group (with setpgid). Thus we introduce a yet
another global sync point -- before it all pgid leaders call
setpgid after it all the others do it.

v2: wait while helpers restored pgid
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-restore.c

@@ -343,6 +343,7 @@ static int restore_one_fake(int pid)
 {
 	/* We should wait here, otherwise last_pid will be changed. */
 	futex_wait_while(&task_entries->start, CR_STATE_FORKING);
+	futex_wait_while(&task_entries->start, CR_STATE_RESTORE_PGID);
 	return 0;
 }
 
@@ -704,13 +705,16 @@ static int restore_task_with_children(void *_arg)
 			exit(1);
 	}
 
-	if (me->state != TASK_HELPER) {
 	futex_dec_and_wake(&task_entries->nr_in_progress);
 	futex_wait_while(&task_entries->start, CR_STATE_FORKING);
-	}
 
 	restore_pgid();
 
+	if (me->state != TASK_HELPER) {
+		futex_dec_and_wake(&task_entries->nr_in_progress);
+		futex_wait_while(&task_entries->start, CR_STATE_RESTORE_PGID);
+	}
+
 	return restore_one_task(me->pid.virt);
 }
 
@@ -774,6 +778,15 @@ static int restore_root_task(struct pstree_item *init, struct cr_options *opts)
 	if (ret < 0)
 		goto out;
 
+	futex_set_and_wake(&task_entries->nr_in_progress, task_entries->nr_tasks);
+	futex_set_and_wake(&task_entries->start, CR_STATE_RESTORE_PGID);
+
+	pr_info("Wait until all tasks restored pgid\n");
+	futex_wait_while_gt(&task_entries->nr_in_progress, 0);
+	ret = (int)futex_get(&task_entries->nr_in_progress);
+	if (ret < 0)
+		goto out;
+
 	futex_set_and_wake(&task_entries->nr_in_progress, task_entries->nr);
 	futex_set_and_wake(&task_entries->start, CR_STATE_RESTORE);
 
@@ -829,6 +842,7 @@ static int prepare_task_entries()
 	}
 	task_entries->nr = 0;
 	task_entries->nr_tasks = 0;
+	task_entries->nr_helpers = 0;
 	futex_set(&task_entries->start, CR_STATE_FORKING);
 
 	return 0;
@@ -848,6 +862,8 @@ static int restore_all_tasks(pid_t pid, struct cr_options *opts)
 	if (prepare_pstree_ids() < 0)
 		return -1;
 
+	futex_set(&task_entries->nr_in_progress, task_entries->nr_tasks + task_entries->nr_helpers);
+
 	return restore_root_task(root_item, opts);
 }
 

include/restorer.h

@@ -211,13 +211,14 @@ struct shmems {
 
 enum {
 	CR_STATE_FORKING,
+	CR_STATE_RESTORE_PGID,
 	CR_STATE_RESTORE,
 	CR_STATE_RESTORE_SIGCHLD,
 	CR_STATE_COMPLETE
 };
 
 struct task_entries {
-	int nr, nr_tasks;
+	int nr, nr_tasks, nr_helpers;
 	futex_t nr_in_progress;
 	futex_t start;
 };

pstree.c

@@ -197,9 +197,6 @@ int prepare_pstree(void)
 		task_entries->nr_tasks++;
 	}
 
-	if (!ret)
-		futex_set(&task_entries->nr_in_progress, task_entries->nr_tasks);
-
 	close(ps_fd);
 	return ret;
 }
@@ -228,6 +225,7 @@ int prepare_pstree_ids(void)
 		helper->state = TASK_HELPER;
 		helper->parent = root_item;
 		list_add_tail(&helper->list, &helpers);
+		task_entries->nr_helpers++;
 
 		pr_info("Add a helper %d for restoring SID %d\n",
 				helper->pid.virt, helper->sid);