minios: refactor xenbus state machine

Implement xenbus_wait_for_state_change and xenbus_switch_state and
change the various frontends to use the two functions and do proper
error checking.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

1 files changed, 49 insertions, 13 deletions

diff --git a/extras/mini-os/blkfront.c b/extras/mini-os/blkfront.c
index 1534747acb..bba1a2ffa6 100644
--- a/extras/mini-os/blkfront.c
+++ b/extras/mini-os/blkfront.c
@@ -149,8 +149,12 @@ again:
         goto abort_transaction;
     }
 
-    err = xenbus_printf(xbt, nodename, "state", "%u",
-            4); /* connected */
+    snprintf(path, sizeof(path), "%s/state", nodename);
+    err = xenbus_switch_state(xbt, path, XenbusStateConnected);
+    if (err) {
+        message = "switching state";
+        goto abort_transaction;
+    }
 
 
     err = xenbus_transaction_end(xbt, 0, &retry);
@@ -179,6 +183,7 @@ done:
     dev->handle = strtoul(strrchr(nodename, '/')+1, NULL, 0);
 
     {
+        XenbusState state;
         char path[strlen(dev->backend) + 1 + 19 + 1];
         snprintf(path, sizeof(path), "%s/mode", dev->backend);
         msg = xenbus_read(XBT_NIL, path, &c);
@@ -196,7 +201,15 @@ done:
 
         xenbus_watch_path_token(XBT_NIL, path, path, &dev->events);
 
-        xenbus_wait_for_value(path, "4", &dev->events);
+        msg = NULL;
+        state = xenbus_read_integer(path);
+        while (msg == NULL && state < XenbusStateConnected)
+            msg = xenbus_wait_for_state_change(path, &state, &dev->events);
+        if (msg != NULL || state != XenbusStateConnected) {
+            printk("backend not available, state=%d\n", state);
+            xenbus_unwatch_path(XBT_NIL, path);
+            goto error;
+        }
 
         snprintf(path, sizeof(path), "%s/info", dev->backend);
         dev->info.info = xenbus_read_integer(path);
@@ -230,25 +243,48 @@ error:
 
 void shutdown_blkfront(struct blkfront_dev *dev)
 {
-    char* err;
-    char *nodename = dev->nodename;
+    char* err = NULL;
+    XenbusState state;
 
     char path[strlen(dev->backend) + 1 + 5 + 1];
+    char nodename[strlen(dev->nodename) + 1 + 5 + 1];
 
     blkfront_sync(dev);
 
-    printk("close blk: backend at %s\n",dev->backend);
+    printk("close blk: backend=%s node=%s\n", dev->backend, dev->nodename);
 
     snprintf(path, sizeof(path), "%s/state", dev->backend);
-    err = xenbus_printf(XBT_NIL, nodename, "state", "%u", 5); /* closing */
-    xenbus_wait_for_value(path, "5", &dev->events);
-
-    err = xenbus_printf(XBT_NIL, nodename, "state", "%u", 6);
-    xenbus_wait_for_value(path, "6", &dev->events);
+    snprintf(nodename, sizeof(nodename), "%s/state", dev->nodename);
 
-    err = xenbus_printf(XBT_NIL, nodename, "state", "%u", 1);
-    xenbus_wait_for_value(path, "2", &dev->events);
+    if ((err = xenbus_switch_state(XBT_NIL, nodename, XenbusStateClosing)) != NULL) {
+        printk("shutdown_blkfront: error changing state to %d: %s\n",
+                XenbusStateClosing, err);
+        goto close;
+    }
+    state = xenbus_read_integer(path);
+    while (err == NULL && state < XenbusStateClosing)
+        err = xenbus_wait_for_state_change(path, &state, &dev->events);
+
+    if ((err = xenbus_switch_state(XBT_NIL, nodename, XenbusStateClosed)) != NULL) {
+        printk("shutdown_blkfront: error changing state to %d: %s\n",
+                XenbusStateClosed, err);
+        goto close;
+    }
+    state = xenbus_read_integer(path);
+    if (state < XenbusStateClosed)
+        xenbus_wait_for_state_change(path, &state, &dev->events);
+
+    if ((err = xenbus_switch_state(XBT_NIL, nodename, XenbusStateInitialising)) != NULL) {
+        printk("shutdown_blkfront: error changing state to %d: %s\n",
+                XenbusStateInitialising, err);
+        goto close;
+    }
+    err = NULL;
+    state = xenbus_read_integer(path);
+    while (err == NULL && (state < XenbusStateInitWait || state >= XenbusStateClosed))
+        err = xenbus_wait_for_state_change(path, &state, &dev->events);
 
+close:
     xenbus_unwatch_path(XBT_NIL, path);
 
     snprintf(path, sizeof(path), "%s/ring-ref", nodename);