Android: Fix deadlock caused by a race between permissions query and IM

Android permissions query blocks Qt main thread. If the input method
was activated before the permissions query started, android would try
to invoke input method before returning back to permissions query.
This will cause a deadlock.

Fix the issue by moving the deadlock counter to Qt core and
incrementing the value before the permissions query. This will prevent
the input method queries to enter Qt main thread.

Fixes: QTBUG-99484
Pick-to: 6.2 6.3 6.3.0
Change-Id: I54ea59578880cde4095c26fa2a6a264c4dc1b7ff
Reviewed-by: Assam Boudjelthia <assam.boudjelthia@qt.io>

src/corelib/kernel/qjnihelpers.cpp

@@ -376,6 +376,18 @@ jobject QtAndroidPrivate::callOnBindListener(jobject intent)
     return nullptr;
 }
 
+Q_GLOBAL_STATIC(QAtomicInt, g_androidDeadlockProtector);
+
+bool QtAndroidPrivate::acquireAndroidDeadlockProtector()
+{
+    return g_androidDeadlockProtector->testAndSetAcquire(0, 1);
+}
+
+void QtAndroidPrivate::releaseAndroidDeadlockProtector()
+{
+    g_androidDeadlockProtector->storeRelease(0);
+}
+
 QT_END_NAMESPACE
 
 Q_CORE_EXPORT jint JNICALL JNI_OnLoad(JavaVM *vm, void *reserved)

src/corelib/kernel/qjnihelpers_p.h

@@ -137,6 +137,9 @@ namespace QtAndroidPrivate
     Q_CORE_EXPORT int acuqireServiceSetup(int flags);
     Q_CORE_EXPORT void setOnBindListener(OnBindListener *listener);
     Q_CORE_EXPORT jobject callOnBindListener(jobject intent);
+
+    Q_CORE_EXPORT bool acquireAndroidDeadlockProtector();
+    Q_CORE_EXPORT void releaseAndroidDeadlockProtector();
 }
 
 #define Q_JNI_FIND_AND_CHECK_CLASS(CLASS_NAME) \

src/corelib/platform/android/qandroidextras.cpp

@@ -1230,7 +1230,7 @@ QtAndroidPrivate::requestPermission(QtAndroidPrivate::PermissionType permission)
     promise->start();
     const auto nativePermissions = nativeStringsFromPermission(permission);
 
-    if (nativePermissions.size() > 0) {
+    if (nativePermissions.size() > 0 && QtAndroidPrivate::acquireAndroidDeadlockProtector()) {
         requestPermissionsInternal(nativePermissions).then(
                     [promise, permission](QFuture<QtAndroidPrivate::PermissionResult> future) {
             auto AuthorizedCount = future.results().count(QtAndroidPrivate::Authorized);
@@ -1242,6 +1242,7 @@ QtAndroidPrivate::requestPermission(QtAndroidPrivate::PermissionType permission)
             } else {
                 promise->addResult(QtAndroidPrivate::Denied, 0);
             }
+            QtAndroidPrivate::releaseAndroidDeadlockProtector();
             promise->finish();
         });
 

src/plugins/platforms/android/CMakeLists.txt

@@ -11,7 +11,7 @@ qt_internal_add_plugin(QAndroidIntegrationPlugin
     DEFAULT_IF ${QT_QPA_DEFAULT_PLATFORM} MATCHES android # special case
     SOURCES
         androidcontentfileengine.cpp androidcontentfileengine.h
-        androiddeadlockprotector.cpp androiddeadlockprotector.h
+        androiddeadlockprotector.h
         androidjniaccessibility.cpp androidjniaccessibility.h
         androidjniclipboard.cpp androidjniclipboard.h
         androidjniinput.cpp androidjniinput.h

src/plugins/platforms/android/androiddeadlockprotector.cpp

@@ -1,43 +0,0 @@
-/****************************************************************************
-**
-** Copyright (C) 2016 The Qt Company Ltd.
-** Contact: https://www.qt.io/licensing/
-**
-** This file is part of the plugins of the Qt Toolkit.
-**
-** $QT_BEGIN_LICENSE:LGPL$
-** Commercial License Usage
-** Licensees holding valid commercial Qt licenses may use this file in
-** accordance with the commercial license agreement provided with the
-** Software or, alternatively, in accordance with the terms contained in
-** a written agreement between you and The Qt Company. For licensing terms
-** and conditions see https://www.qt.io/terms-conditions. For further
-** information use the contact form at https://www.qt.io/contact-us.
-**
-** GNU Lesser General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU Lesser
-** General Public License version 3 as published by the Free Software
-** Foundation and appearing in the file LICENSE.LGPL3 included in the
-** packaging of this file. Please review the following information to
-** ensure the GNU Lesser General Public License version 3 requirements
-** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
-**
-** GNU General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU
-** General Public License version 2.0 or (at your option) the GNU General
-** Public license version 3 or any later version approved by the KDE Free
-** Qt Foundation. The licenses are as published by the Free Software
-** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
-** included in the packaging of this file. Please review the following
-** information to ensure the GNU General Public License requirements will
-** be met: https://www.gnu.org/licenses/gpl-2.0.html and
-** https://www.gnu.org/licenses/gpl-3.0.html.
-**
-** $QT_END_LICENSE$
-**
-****************************************************************************/
-
-#include "androiddeadlockprotector.h"
-
-QAtomicInt AndroidDeadlockProtector::s_blocked(0);
-

src/plugins/platforms/android/androiddeadlockprotector.h

@@ -40,31 +40,25 @@
 #ifndef ANDROID_DEADLOCKPROTECTOR_H
 #define ANDROID_DEADLOCKPROTECTOR_H
 
-#include <QAtomicInt>
+#include <QtCore/private/qjnihelpers_p.h>
 
 QT_BEGIN_NAMESPACE
 
 class AndroidDeadlockProtector
 {
 public:
-    AndroidDeadlockProtector()
-        : m_acquired(0)
-    {
-    }
-
     ~AndroidDeadlockProtector() {
         if (m_acquired)
-            s_blocked.storeRelease(0);
+            QtAndroidPrivate::releaseAndroidDeadlockProtector();
     }
 
     bool acquire() {
-        m_acquired = s_blocked.testAndSetAcquire(0, 1);
+        m_acquired = QtAndroidPrivate::acquireAndroidDeadlockProtector();
         return m_acquired;
     }
 
 private:
-    static QAtomicInt s_blocked;
-    int m_acquired;
+    bool m_acquired = false;
 };
 
 QT_END_NAMESPACE