Allow dumps of stopped multithreaded processes

CRIU can handle stopped multithreaded processes when all threads
are stopped. Refine the check to allow this case.
Signed-off-by: Christopher Covington <cov@codeaurora.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-dump.c

@@ -833,7 +833,7 @@ static pid_t item_ppid(const struct pstree_item *item)
 static int seize_threads(struct pstree_item *item,
 				struct pid *threads, int nr_threads)
 {
-	int i = 0, ret, j, nr_inprogress;
+	int i = 0, ret, j, nr_inprogress, nr_stopped = 0;
 
 	if ((item->state == TASK_DEAD) && (nr_threads > 1)) {
 		pr_err("Zombies with threads are not supported\n");
@@ -889,11 +889,15 @@ static int seize_threads(struct pstree_item *item,
 		}
 
 		if (ret == TASK_STOPPED) {
-			pr_err("Stopped threads not supported\n");
-			goto err;
+			nr_stopped++;
 		}
 	}
 
+	if (nr_stopped && nr_stopped != nr_inprogress) {
+		pr_err("Individually stopped threads not supported\n");
+		goto err;
+	}
+
 	return nr_inprogress;
 err:
 	return -1;