[Xen-devel] [PATCH] xl: Check for dependencies in xl

[Kamala Narasimhan <kamala.narasimhan@xxxxxxxxx>]

If I fail to start xencommons before starting a vm, I get a non
obvious "failed to free memory for the domain" error!  This patch
checks for dependencies when xl is invoked.

Note:  Currently I am checking for xenstore daemon only.  More checks
could be added if necessary.  Also, I am performing the check
irrespective of the kind of command being invoked through xl.
Example. xl info, list etc.  doesn't require that xenstored be
running.  But expecting xenstored be running before invoking the
toolstack seem like a reasonable expectation in general.  Please
consider this for inclusion or feel free to tweak it as necessary.

Signed-off-by: Kamala Narasimhan <kamala.narasimhan@xxxxxxxxxx>

Kamala

diff -r ce208811f540 tools/libxl/xl.c
--- a/tools/libxl/xl.c  Thu Jan 13 01:26:44 2011 +0000
+++ b/tools/libxl/xl.c  Thu Jan 13 11:26:35 2011 -0500
@@ -74,6 +74,27 @@ static void parse_global_config(const ch

     xlu_cfg_destroy(config);
 }
+
+static int check_dependencies(void)
+{
+    struct xs_handle *xsh;
+
+    xsh = xs_daemon_open();
+    if ( !xsh )
+    {
+        fprintf(stderr, "xs_daemon_open failed!\n");
+        return 0;
+    }
+
+    if ( xs_read(xsh, XBT_NULL, "/local/domain/0/name", NULL) == NULL )
+    {
+        fprintf(stderr, "Xenstore daemon is not running or not
initialized properly!\n");
+        return 0;
+    }
+
+    xs_daemon_close(xsh);
+    return 1;
+}

 int main(int argc, char **argv)
 {
@@ -103,6 +124,9 @@ int main(int argc, char **argv)
         exit(1);
     }
     opterr = 0;
+
+    if ( !check_dependencies() )
+        exit(1);

     logger = xtl_createlogger_stdiostream(stderr, minmsglevel,  0);
     if (!logger) exit(1);

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