restore: shmem -- Don't poll, use wait helpers instead

Signed-off-by: Andrey Vagin <avagin@openvz.org>
[gorcunov: A few tuneups]
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>

cr-restore.c

@@ -144,33 +144,27 @@ static void shmem_update_real_pid(int vpid, int rpid)
 
 static int shmem_wait_and_open(struct shmem_info *si)
 {
-	unsigned long time = 1000;
+	unsigned long time = 1;
 	char path[128];
+	int ret;
 
-	sleep(1);
-
-	while (si->real_pid == 0)
-		usleep(time);
+	cr_wait_until(&si->lock, 1);
 
 	sprintf(path, "/proc/%d/map_files/%lx-%lx",
 		si->real_pid, si->start, si->end);
 
-	while (1) {
-		int ret = open(path, O_RDWR);
-		if (ret >= 0)
-			return ret;
+	pr_info("Waiting for [%s] to appear\n", path);
 
-		if (ret < 0 && errno != ENOENT) {
-			pr_perror("     %d: Can't stat shmem at %s\n",
-				  si->real_pid, path);
-			return -1;
-		}
+	ret = open(path, O_RDWR);
+	if (ret >= 0)
+		return ret;
 
-		pr_info("Waiting for [%s] to appear\n", path);
-		if (time < 20000000)
-			time <<= 1;
-		usleep(time);
+	if (ret < 0) {
+		pr_perror("     %d: Can't stat shmem at %s\n",
+			  si->real_pid, path);
+		return -1;
 	}
+	return 0;
 }
 
 static int collect_shmem(int pid, struct shmem_entry *e)

include/restorer.h

@@ -296,6 +296,7 @@ struct shmem_info {
 	unsigned long	shmid;
 	int		pid;
 	int		real_pid;
+	u32		lock;		/* futex */
 };
 
 struct shmems {

restorer.c

@@ -277,6 +277,23 @@ self_len_end:
 
 			if (vma_entry->fd != -1UL)
 				sys_close(vma_entry->fd);
+
+			if (vma_entry_is(vma_entry, VMA_ANON_SHARED) &&
+			    vma_entry->fd == -1UL) {
+				struct shmem_info *entry;
+
+				entry = find_shmem_by_pid(args->shmems,
+							  vma_entry->start,
+							  sys_getpid());
+				if (!entry) {
+					write_num_n(__LINE__);
+					write_hex_n(vma_entry->start);
+					goto core_restore_end;
+				}
+
+				cr_wait_set(&entry->lock, 1);
+			}
+
 		}
 
 		/*