[CRIU] [PATCH v3 03/55] cr-restore: Open transport socket earlier

[Kirill Tkhai]

I need named socket to communicate with pid_ns helpers
(see next patches) and receive answer from them
(it's impossible to send answer to unnamed socket).
As we already have transport socket, we'll reuse it
for the above goal too.

This patch makes transport sockets be created before
creation of children tasks. Also, now it's created
not only for alive tasks.

(It seems, it won't be good to make futex_lock and
futex_mutex union unless we define one as equal type
to other using typedef, but anyway I'd happy to hear
your opinions).

Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 criu/cr-restore.c       |    6 +++---
 criu/files.c            |   20 ++++++++++++--------
 criu/include/rst_info.h |    1 +
 criu/pstree.c           |    2 +-
 4 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/criu/cr-restore.c b/criu/cr-restore.c
index 7842e169e..3ec1cf1dc 100644
--- a/criu/cr-restore.c
+++ b/criu/cr-restore.c
@@ -1438,6 +1438,9 @@ static int restore_task_with_children(void *_arg)
 		BUG();
 	}
 
+	if (open_transport_socket())
+		goto err;
+
 	if (create_children_and_session())
 		goto err;
 
@@ -1457,9 +1460,6 @@ static int restore_task_with_children(void *_arg)
 		fini_restore_mntns();
 	}
 
-	if (open_transport_socket())
-		return -1;
-
 	if (restore_finish_stage(task_entries, CR_STATE_FORKING) < 0)
 		goto err;
 
diff --git a/criu/files.c b/criu/files.c
index 07cc9cc1d..52f2d5513 100644
--- a/criu/files.c
+++ b/criu/files.c
@@ -1327,6 +1327,7 @@ int shared_fdt_prepare(struct pstree_item *item)
 
 		rsti(parent)->fdt = fdt;
 
+		mutex_init(&fdt->fdt_mutex);
 		futex_init(&fdt->fdt_lock);
 		fdt->nr = 1;
 		fdt->pid = vpid(parent);
@@ -1637,29 +1638,32 @@ int open_transport_socket(void)
 	struct fdt *fdt = rsti(current)->fdt;
 	pid_t pid = vpid(current);
 	struct sockaddr_un saddr;
-	int sock, slen;
+	int sock, slen, ret = -1;
 
-	if (!task_alive(current) || (fdt && fdt->pid != pid))
-		return 0;
+	if (fdt)
+		mutex_lock(&fdt->fdt_mutex);
 
 	sock = socket(PF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC, 0);
 	if (sock < 0) {
 		pr_perror("Can't create socket");
-		return -1;
+		goto out;
 	}
 
 	transport_name_gen(&saddr, &slen, pid);
 	if (bind(sock, (struct sockaddr *)&saddr, slen) < 0) {
 		pr_perror("Can't bind transport socket %s", saddr.sun_path + 1);
 		close(sock);
-		return -1;
+		goto out;
 	}
 
 	if (install_service_fd(TRANSPORT_FD_OFF, sock) < 0) {
 		close(sock);
-		return -1;
+		goto out;
 	}
 	close(sock);
-
-	return 0;
+	ret = 0;
+out:
+	if (fdt)
+		mutex_unlock(&fdt->fdt_mutex);
+	return ret;
 }
diff --git a/criu/include/rst_info.h b/criu/include/rst_info.h
index 92dfc9d93..1860c21fc 100644
--- a/criu/include/rst_info.h
+++ b/criu/include/rst_info.h
@@ -21,6 +21,7 @@ struct fdt {
 	 * The fdt table was restrored, if fdt_lock is equal to nr + 1
 	 */
 	futex_t			fdt_lock;
+	mutex_t			fdt_mutex;
 };
 
 struct _MmEntry;
diff --git a/criu/pstree.c b/criu/pstree.c
index b21e2747d..93c90ee2e 100644
--- a/criu/pstree.c
+++ b/criu/pstree.c
@@ -234,7 +234,7 @@ struct pstree_item *__alloc_pstree_item(bool rst)
 void init_pstree_helper(struct pstree_item *ret)
 {
 	ret->pid->state = TASK_HELPER;
-	rsti(ret)->clone_flags = CLONE_FILES | CLONE_FS;
+	rsti(ret)->clone_flags = 0;
 	task_entries->nr_helpers++;
 }