tdf#114025 framework: avoid deadlock between Desktop init ...

... and SolarMutex: the problem is that rtl::StaticWithArg will
first lock the implicit mutex of the C++11 static variable, and
then the SolarMutex.

So if one thread creates the Desktop singleton with SolarMutex
locked and another thread without SolarMutex locked, this can
deadlock.

If we use rtl_Instance directly with SolarMutex, then there is
still a static variable, but the SolarMutex will always be locked
first, preventing this deadlock.

Change-Id: Ibd37fdfa96a4a2b57f661be3814dd597eb52d338
Reviewed-on: https://gerrit.libreoffice.org/45508Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Jenkins <ci@libreoffice.org>

framework/source/services/desktop.cxx

@@ -1796,10 +1796,30 @@ struct Instance {
     rtl::Reference<framework::Desktop> instance;
 };
 
-struct Singleton:
-    public rtl::StaticWithArg<
-        Instance, css::uno::Reference<css::uno::XComponentContext>, Singleton>
-{};
+struct InstanceInit {
+    Instance * operator() (css::uno::Reference<css::uno::XComponentContext> const& xContext) {
+        static Instance instance(xContext);
+        return &instance;
+    }
+};
+
+struct GetSolarMutex {
+    comphelper::SolarMutex * operator() ()
+    {
+        return &Application::GetSolarMutex();
+    }
+};
+
+Instance & getInstance(css::uno::Reference<css::uno::XComponentContext> const& xContext)
+{
+    // tdf#114025 init with SolarMutex to avoid deadlock
+    return *rtl_Instance<Instance,
+                         InstanceInit,
+                         osl::Guard<comphelper::SolarMutex>,
+                         GetSolarMutex,
+                         css::uno::Reference<css::uno::XComponentContext> const>
+                ::create(InstanceInit(), GetSolarMutex(), xContext);
+}
 
 }
 
@@ -1808,7 +1828,7 @@ com_sun_star_comp_framework_Desktop_get_implementation(
     css::uno::XComponentContext *context,
     css::uno::Sequence<css::uno::Any> const &)
 {
-    return cppu::acquire(Singleton::get(context).instance.get());
+    return cppu::acquire(getInstance(context).instance.get());
 }
 
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