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>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/corelib/kernel/qjnihelpers.cpp b/src/corelib/kernel/qjnihelpers.cpp
index b2a5dc7441..73b15ce46a 100644
--- a/src/corelib/kernel/qjnihelpers.cpp
+++ b/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)