[libvirt] [PATCH 3/4] Cache the presence of machine1 service

[Ján Tomko]

After the system has been booted, it should not change.

Cache the return value of virSystemdHasCreateMachine.
Allow starting and terminating machines with just one
DBus call, instead of three, reducing the chance of
the call timing out.

Also introduce a small function for resetting the cache
to be used in tests.
---
 src/libvirt_private.syms  |  1 +
 src/util/virsystemd.c     | 28 ++++++++++++++++++++++++++--
 src/util/virsystemdpriv.h | 33 +++++++++++++++++++++++++++++++++
 tests/virsystemdtest.c    |  4 ++++
 4 files changed, 64 insertions(+), 2 deletions(-)
 create mode 100644 src/util/virsystemdpriv.h

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 07a3533..738c3c8 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -2557,6 +2557,7 @@ virSystemdCanHibernate;
 virSystemdCanHybridSleep;
 virSystemdCanSuspend;
 virSystemdCreateMachine;
+virSystemdCreateMachineResetCachedValue;
 virSystemdGetMachineNameByPID;
 virSystemdMakeMachineName;
 virSystemdMakeScopeName;
diff --git a/src/util/virsystemd.c b/src/util/virsystemd.c
index d7a4e78..5982bc4 100644
--- a/src/util/virsystemd.c
+++ b/src/util/virsystemd.c
@@ -26,6 +26,9 @@
 # include <sys/un.h>
 #endif
 
+#define __VIR_SYSTEMD_PRIV_H_ALLOW__ 1
+#include "virsystemdpriv.h"
+
 #include "virsystemd.h"
 #include "viratomic.h"
 #include "virbuffer.h"
@@ -182,6 +185,15 @@ virSystemdMakeMachineName(const char *drivername,
     return machinename;
 }
 
+static int virSystemdCreateMachineCachedValue = -1;
+
+/* Reset the cache from tests for testing the underlying dbus calls
+ * as well */
+void virSystemdCreateMachineResetCachedValue(void)
+{
+    virSystemdCreateMachineCachedValue = -1;
+}
+
 /* -2 = machine1 is not supported on this machine
  * -1 = error
  *  0 = machine1 is available
@@ -190,10 +202,22 @@ static int
 virSystemdHasCreateMachine(void)
 {
     int ret;
-    if ((ret = virDBusIsServiceEnabled("org.freedesktop.machine1")) < 0)
+    int val;
+
+    val = virAtomicIntGet(&virSystemdCreateMachineCachedValue);
+    if (val != -1)
+        return val;
+
+    if ((ret = virDBusIsServiceEnabled("org.freedesktop.machine1")) < 0) {
+        if (ret == -2)
+            virAtomicIntSet(&virSystemdCreateMachineCachedValue, -2);
         return ret;
+    }
 
-    return virDBusIsServiceRegistered("org.freedesktop.systemd1");
+    if ((ret = virDBusIsServiceRegistered("org.freedesktop.systemd1")) == -1)
+        return ret;
+    virAtomicIntSet(&virSystemdCreateMachineCachedValue, ret);
+    return ret;
 }
 
 
diff --git a/src/util/virsystemdpriv.h b/src/util/virsystemdpriv.h
new file mode 100644
index 0000000..413bc8b
--- /dev/null
+++ b/src/util/virsystemdpriv.h
@@ -0,0 +1,33 @@
+/*
+ * virsystemdpriv.h: Functions for testing virSystemd APIs
+ *
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef __VIR_SYSTEMD_PRIV_H_ALLOW__
+# error "virsystemdpriv.h may only be included by virsystemd.c or test suites"
+#endif
+
+#ifndef __VIR_SYSTEMD_PRIV_H__
+# define __VIR_SYSTEMD_PRIV_H__
+
+# include "virsystemd.h"
+
+void virSystemdCreateMachineResetCachedValue(void);
+
+#endif /* __VIR_SYSTEMD_PRIV_H__ */
diff --git a/tests/virsystemdtest.c b/tests/virsystemdtest.c
index 177cccc..eca6e84 100644
--- a/tests/virsystemdtest.c
+++ b/tests/virsystemdtest.c
@@ -27,6 +27,9 @@
 # include <stdlib.h>
 # include <dbus/dbus.h>
 
+# define __VIR_SYSTEMD_PRIV_H_ALLOW__ 1
+# include "virsystemdpriv.h"
+
 # include "virsystemd.h"
 # include "virdbus.h"
 # include "virlog.h"
@@ -522,6 +525,7 @@ mymain(void)
     do {                                                                \
         if (virTestRun(_name, func, NULL) < 0)                          \
             ret = -1;                                                   \
+        virSystemdCreateMachineResetCachedValue();                      \
     } while (0)
 
     DO_TEST("Test create container ", testCreateContainer);
-- 
2.10.2