framework: lock the solar mutex in loadComponentFromURL() with OnMainThread

Regression from commit 2dc3a6c273cb82506842864481d78df7294debbf
(framework: allow loading a component on the main thread, 2018-12-19),
which was a forward-port from a 5.4-based vendor branch, where this was
(it turns out) just working by accident, but never on master.

It can happen that loadComponentFromURL() is invoked on a thread, which
does not own the solar mutex. Then once
vcl::SolarThreadExecutor::execute() is called, it'll try to release the
solar mutex. But SolarMutexReleaser is unsafe: it'll release the mutex
even if it is owned by an other thread.

To make this a bit more safer, it'll abort in
comphelper::SolarMutex::doRelease(), in case the current thread doesn't
have the mutex already.

Fix the problem by taking the solar mutex in loadComponentFromURL():
this is meant to cause no performance problems, since the actual
importers typically start with taking the solar mutex anyway. Taking it
earlier would be problematic, since this can be invoked by UNO clients
directly. Taking it later in vcl/ would be also unusual: typically vcl
just asserts that the solar mutex is locked, doesn't take it itself.

Change-Id: I752006a91f16a02254d1b5ac6301100ab282630b
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/103264
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Tested-by: Jenkins

1 files changed, 133 insertions, 0 deletions

diff --git a/framework/qa/cppunit/services.cxx b/framework/qa/cppunit/services.cxx
new file mode 100644
index 000000000000..93d05ff65ca5
--- /dev/null
+++ b/framework/qa/cppunit/services.cxx
@@ -0,0 +1,133 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <test/bootstrapfixture.hxx>
+#include <unotest/macros_test.hxx>
+
+#include <com/sun/star/frame/Desktop.hpp>
+#include <com/sun/star/frame/XFrame.hpp>
+#include <com/sun/star/frame/XComponentLoader.hpp>
+#include <com/sun/star/frame/FrameSearchFlag.hpp>
+
+#include <comphelper/propertyvalue.hxx>
+#include <salhelper/thread.hxx>
+#include <vcl/svapp.hxx>
+#include <vcl/scheduler.hxx>
+#include <vcl/wrkwin.hxx>
+
+using namespace ::com::sun::star;
+
+namespace
+{
+/// Covers framework/source/services/ fixes.
+class Test : public test::BootstrapFixture, public unotest::MacrosTest
+{
+protected:
+    uno::Reference<lang::XComponent> mxComponent;
+
+public:
+    void setUp() override;
+    void tearDown() override;
+    uno::Reference<lang::XComponent>& getComponent() { return mxComponent; }
+};
+
+void Test::setUp()
+{
+    test::BootstrapFixture::setUp();
+
+    mxDesktop.set(frame::Desktop::create(mxComponentContext));
+}
+
+void Test::tearDown()
+{
+    if (mxComponent.is())
+        mxComponent->dispose();
+
+    test::BootstrapFixture::tearDown();
+}
+
+/// Invokes XFrameImpl::loadComponentFromURL() on a thread.
+class TestThread : public salhelper::Thread
+{
+    uno::Reference<frame::XComponentLoader> mxComponentLoader;
+    uno::Reference<lang::XComponent>& mrComponent;
+
+public:
+    TestThread(const uno::Reference<frame::XComponentLoader>& xComponentLoader,
+               uno::Reference<lang::XComponent>& rComponent);
+    void execute() override;
+};
+
+TestThread::TestThread(const uno::Reference<frame::XComponentLoader>& xComponentLoader,
+                       uno::Reference<lang::XComponent>& rComponent)
+    : salhelper::Thread("TestThread")
+    , mxComponentLoader(xComponentLoader)
+    , mrComponent(rComponent)
+{
+}
+
+void TestThread::execute()
+{
+    sal_Int32 nSearchFlags = frame::FrameSearchFlag::AUTO;
+    uno::Sequence<beans::PropertyValue> aArguments = {
+        comphelper::makePropertyValue("OnMainThread", true),
+    };
+    // Note how this is invoking loadComponentFromURL() on a frame, not on the desktop, as usual.
+    mrComponent = mxComponentLoader->loadComponentFromURL("private:factory/swriter", "_self",
+                                                          nSearchFlags, aArguments);
+}
+
+CPPUNIT_TEST_FIXTURE(Test, testLoadComponentFromURL)
+{
+    // Without the accompanying fix in place, this test would have failed with:
+    // thread 1: comphelper::SolarMutex::doRelease end: m_nCount is 1
+    // thread 2: vcl::SolarThreadExecutor::execute: before SolarMutexReleaser ctor
+    // thread 2: comphelper::SolarMutex::doRelease start: m_nCount is 1, bUnlockAll is 1
+    // thread 2: comphelper::SolarMutex::doRelease: failed IsCurrentThread() check, will abort
+    // Notice how thread 2 attempts to release the solar mutex while thread 1 holds it.
+
+    // Create a default window, so by the time the thread would post a user event, it doesn't need
+    // the solar mutex to process a SendMessageW() call on Windows.
+    VclPtrInstance<WorkWindow> xWindow(nullptr, WB_APP | WB_STDWORK);
+    // Variable is not used, it holds the default window.
+    (void)xWindow;
+
+    rtl::Reference<TestThread> xThread;
+    {
+        // Start the thread that will load the component, but hold the solar mutex for now, so we
+        // can see if it blocks.
+        SolarMutexGuard guard;
+        uno::Reference<frame::XFrame> xFrame = mxDesktop->findFrame("_blank", /*nSearchFlags=*/0);
+        uno::Reference<frame::XComponentLoader> xComponentLoader(xFrame, uno::UNO_QUERY);
+        xThread = new TestThread(xComponentLoader, getComponent());
+        xThread->launch();
+        // If loadComponentFromURL() doesn't lock the solar mutex, the test will abort here.
+        osl::Thread::wait(std::chrono::seconds(1));
+    }
+    {
+        // Now release the solar mutex, so the thread can post the task on the main loop.
+        SolarMutexReleaser releaser;
+        osl::Thread::wait(std::chrono::seconds(1));
+    }
+    {
+        // Spin the main loop.
+        SolarMutexGuard guard;
+        Scheduler::ProcessEventsToIdle();
+    }
+    {
+        // Stop the thread.
+        SolarMutexReleaser releaser;
+        xThread->join();
+    }
+}
+}
+
+CPPUNIT_PLUGIN_IMPLEMENT();
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */