restore: new mechanism to sync tasks

Now we have only one mutex nr_in_progress, it says how many
tasks are not restored yet. A negative value signs that someone
failed.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>

cr-restore.c

@@ -395,7 +395,7 @@ static int prepare_shared(int ps_fd)
 		return -1;
 	}
 	task_entries->nr = 0;
-	task_entries->start  = 0;
+	task_entries->start = CR_STATE_RESTORE;
 
 	pipes = mmap(NULL, 4096, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANON, 0, 0);
 	if (pipes == MAP_FAILED) {
@@ -433,6 +433,8 @@ static int prepare_shared(int ps_fd)
 		lseek(ps_fd, e.nr_children * sizeof(u32) + e.nr_threads * sizeof(u32), SEEK_CUR);
 	}
 
+	task_entries->nr_in_progress = task_entries->nr;
+
 	lseek(ps_fd, sizeof(u32), SEEK_SET);
 
 	show_saved_shmems();
@@ -1231,6 +1233,9 @@ static int restore_root_task(int fd, bool detach)
 	if (ret < 0)
 		return -1;
 
+	pr_info("Wait until all tasks are restored");
+	cr_wait_until(&task_entries->nr_in_progress, 0);
+
 	for (i = 0; i < task_entries->nr; i++) {
 		pr_info("Wait while the task %d restored\n",
 				task_entries->entries[i].pid);
@@ -1238,7 +1243,7 @@ static int restore_root_task(int fd, bool detach)
 	}
 
 	pr_info("Go on!!!\n");
-	cr_wait_set(&task_entries->start, 1);
+	cr_wait_set(&task_entries->start, CR_STATE_COMPLETE);
 
 	if (!detach)
 		wait(NULL);

include/restorer.h

@@ -193,6 +193,11 @@ struct shmems {
 
 #define TASK_ENTRIES_SIZE 4096
 
+enum {
+	CR_STATE_RESTORE,
+	CR_STATE_COMPLETE
+};
+
 struct task_entry {
 	int pid;
 	u32 done; // futex
@@ -200,6 +205,7 @@ struct task_entry {
 
 struct task_entries {
 	int nr;
+	u32 nr_in_progress;
 	u32 start; //futex
 	struct task_entry entries[0];
 };

restorer.c

@@ -505,10 +505,11 @@ long restore_task(struct task_restore_core_args *args)
 	}
 
 	task_entry = task_get_entry(args->task_entries, my_pid);
+	cr_wait_dec(&args->task_entries->nr_in_progress);
 	cr_wait_set(&task_entry->done, 1);
 	write_num(sys_getpid());
 	write_string_n(": Restored");
-	cr_wait_while(&args->task_entries->start, 0);
+	cr_wait_while(&args->task_entries->start, CR_STATE_RESTORE);
 
 	ret = sys_munmap(args->task_entries, TASK_ENTRIES_SIZE);
 	if (ret < 0) {