Revert "Add categorized logging of delete later machinery"

This reverts commit c3a2b9f35a9a12ff3c6f5f0d11844de161b47c2a.

Unfortunately, some of the log messages happen WAY too late at process
exit time, when QtCore is unloading. In particular, the worst offender
is the one in QThreadPrivate::finish(), which is called after the last
QObject in the thread that called ::exit() was getting destroyed. This
implies we have Static (De)Initialization Order Fiascos happening (the
logging recurses into qlocale.cpp and the defaultLocalePrivate global
static has already been destroyed).

I need to revert this commit in order to fix QThreadData destruction.
The functionality is welcome back in QtCore once the fixes are in, so
long as whoever does it fixes the issues we're seeing in the CI (and I
can't reproduce on my development machine). I've created QTBUG-132429 to
track the reversal and see if the functionality can be brought back in.

Task-number: QTBUG-120124
Task-number: QTBUG-132429
Pick-to: 6.9 6.8
Change-Id: Iecf8f14529c7a2bb2185fffdfd328066098826b1
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/corelib/kernel/qcoreapplication.cpp

@@ -115,10 +115,6 @@
 
 QT_BEGIN_NAMESPACE
 
-#ifndef QT_NO_QOBJECT
-Q_LOGGING_CATEGORY(lcDeleteLater, "qt.core.qobject.deletelater")
-#endif
-
 using namespace Qt::StringLiterals;
 
 Q_TRACE_PREFIX(qtcore,
@@ -1481,8 +1477,6 @@ void QCoreApplicationPrivate::execCleanup()
 {
     threadData.loadRelaxed()->quitNow = false;
     in_exec = false;
-
-    qCDebug(lcDeleteLater) << "Sending deferred delete events as part of exec cleanup";
     QCoreApplication::sendPostedEvents(nullptr, QEvent::DeferredDelete);
 }
 
@@ -1853,37 +1847,16 @@ void QCoreApplicationPrivate::sendPostedEvents(QObject *receiver, int event_type
             //    events posted by the current event loop; or
             // 3) if the event was posted before the outermost event loop.
 
-            const auto *event = static_cast<QDeferredDeleteEvent *>(pe.event);
-            qCDebug(lcDeleteLater) << "Processing deferred delete event for" << pe.receiver
-                << "with loop level" << event->loopLevel() << "and scope level" << event->scopeLevel();
-
-            qCDebug(lcDeleteLater) << "Checking" << data->thread << "with loop level"
-                << data->loopLevel << "and scope level" << data->scopeLevel;
-
-            bool allowDeferredDelete = false;
-            if (event->loopLevel() == 0 && data->loopLevel > 0) {
-                qCDebug(lcDeleteLater) << "Event was posted outside outermost event loop"
-                    << "and current thread has an event loop running.";
-                allowDeferredDelete = true;
-            } else {
-                const int totalEventLevel = event->loopLevel() + event->scopeLevel();
-                const int totalThreadLevel = data->loopLevel + data->scopeLevel;
-
-                if (totalEventLevel > totalThreadLevel) {
-                    qCDebug(lcDeleteLater) << "Combined levels of event" << totalEventLevel
-                        << "is higher than thread" << totalThreadLevel;
-                    allowDeferredDelete = true;
-                } else if (event_type == QEvent::DeferredDelete && totalEventLevel == totalThreadLevel) {
-                    qCDebug(lcDeleteLater) << "Explicit send of DeferredDelete and"
-                        << "levels of event" << totalEventLevel
-                        << "is same as thread" << totalThreadLevel;
-                    allowDeferredDelete = true;
-                }
-            }
+            const int eventLoopLevel = static_cast<QDeferredDeleteEvent *>(pe.event)->loopLevel();
+            const int eventScopeLevel = static_cast<QDeferredDeleteEvent *>(pe.event)->scopeLevel();
 
+            const bool postedBeforeOutermostLoop = eventLoopLevel == 0;
+            const bool allowDeferredDelete =
+                (eventLoopLevel + eventScopeLevel > data->loopLevel + data->scopeLevel
+                 || (postedBeforeOutermostLoop && data->loopLevel > 0)
+                 || (event_type == QEvent::DeferredDelete
+                     && eventLoopLevel + eventScopeLevel == data->loopLevel + data->scopeLevel));
             if (!allowDeferredDelete) {
-                qCDebug(lcDeleteLater) << "Failed conditions for deferred delete. Deferring again";
-
                 // cannot send deferred delete
                 if (!event_type && !receiver) {
                     // we must copy it first; we want to re-post the event
@@ -1900,8 +1873,6 @@ void QCoreApplicationPrivate::sendPostedEvents(QObject *receiver, int event_type
                     data->postEventList.addEvent(pe_copy);
                 }
                 continue;
-            } else {
-                qCDebug(lcDeleteLater) << "Sending deferred delete to" << pe.receiver;
             }
         }
 

src/corelib/kernel/qcoreapplication_p.h

@@ -25,7 +25,6 @@
 #include "QtCore/qsettings.h"
 #endif
 #ifndef QT_NO_QOBJECT
-#include <qloggingcategory.h>
 #include "private/qobject_p.h"
 #include "private/qlocking_p.h"
 #endif
@@ -36,10 +35,6 @@
 
 QT_BEGIN_NAMESPACE
 
-#ifndef QT_NO_QOBJECT
-Q_DECLARE_LOGGING_CATEGORY(lcDeleteLater)
-#endif
-
 typedef QList<QTranslator*> QTranslatorList;
 
 class QAbstractEventDispatcher;

src/corelib/kernel/qeventloop.cpp

@@ -155,9 +155,6 @@ int QEventLoop::exec(ProcessEventsFlags flags)
             auto threadData = d->threadData.loadRelaxed();
             ++threadData->loopLevel;
             threadData->eventLoops.push(d->q_func());
-            qCDebug(lcDeleteLater) << "Increased" << threadData->thread
-                      << "loop level to" << threadData->loopLevel
-                      << "with leaf loop now" << threadData->eventLoops.last();
 
             locker.unlock();
         }
@@ -176,12 +173,6 @@ int QEventLoop::exec(ProcessEventsFlags flags)
             Q_UNUSED(eventLoop); // --release warning
             d->inExec = false;
             --threadData->loopLevel;
-
-            qCDebug(lcDeleteLater) << "Decreased" << threadData->thread
-                      << "loop level to" << threadData->loopLevel
-                      << "with leaf loop now" << (threadData->eventLoops.isEmpty()
-                        ? nullptr : threadData->eventLoops.last());
-
         }
     };
     LoopReference ref(d, locker);

src/corelib/kernel/qobject.cpp

@@ -1413,7 +1413,6 @@ bool QObject::event(QEvent *e)
         break;
 
     case QEvent::DeferredDelete:
-        qCDebug(lcDeleteLater) << "Deferred deleting" << this;
         delete this;
         break;
 
@@ -2464,10 +2463,8 @@ void QObject::deleteLater()
     // as long as we're not guarding every access to the bit field.
 
     Q_D(QObject);
-    if (d->deleteLaterCalled) {
-        qCDebug(lcDeleteLater) << "Skipping deleteLater for already deferred object" << this;
+    if (d->deleteLaterCalled)
         return;
-    }
 
     d->deleteLaterCalled = true;
 
@@ -2493,16 +2490,10 @@ void QObject::deleteLater()
         // non-conformant code path, and our best guess is that the scope level
         // should be 1. (Loop level 0 is special: it means that no event loops
         // are running.)
-        if (scopeLevel == 0 && loopLevel != 0) {
-            qCDebug(lcDeleteLater) << "Delete later called with scope level 0"
-                << "but loop level is > 0. Assuming scope is 1";
+        if (scopeLevel == 0 && loopLevel != 0)
             scopeLevel = 1;
-        }
     }
 
-    qCDebug(lcDeleteLater) << "Posting deferred delete for" << this
-        << "with loop level" << loopLevel << "and scope level" << scopeLevel;
-
     eventListLocker.unlock();
     QCoreApplication::postEvent(this,
         new QDeferredDeleteEvent(loopLevel, scopeLevel));

src/corelib/kernel/qtranslator.cpp

@@ -19,6 +19,7 @@
 #include "qtranslator_p.h"
 #include "qlocale.h"
 #include "qlogging.h"
+#include "qloggingcategory.h"
 #include "qdebug.h"
 #include "qendian.h"
 #include "qresource.h"

src/corelib/thread/qthread.cpp

@@ -131,21 +131,6 @@ void QAdoptedThread::run()
 }
 #endif
 
-QScopedScopeLevelCounter::QScopedScopeLevelCounter(QThreadData *threadData)
-    : threadData(threadData)
-{
-    ++threadData->scopeLevel;
-    qCDebug(lcDeleteLater) << "Increased" << threadData->thread
-                      << "scope level to" << threadData->scopeLevel;
-}
-
-QScopedScopeLevelCounter::~QScopedScopeLevelCounter()
-{
-    --threadData->scopeLevel;
-    qCDebug(lcDeleteLater) << "Decreased" << threadData->thread
-                      << "scope level to" << threadData->scopeLevel;
-}
-
 #if QT_CONFIG(thread)
 /*
   QThreadPrivate

src/corelib/thread/qthread_p.h

@@ -379,8 +379,11 @@ class QScopedScopeLevelCounter
 {
     QThreadData *threadData;
 public:
-    QScopedScopeLevelCounter(QThreadData *threadData);
-    ~QScopedScopeLevelCounter();
+    inline QScopedScopeLevelCounter(QThreadData *threadData)
+        : threadData(threadData)
+    { ++threadData->scopeLevel; }
+    inline ~QScopedScopeLevelCounter()
+    { --threadData->scopeLevel; }
 };
 
 // thread wrapper for the main() thread

src/corelib/thread/qthread_unix.cpp

@@ -8,6 +8,7 @@
 #include <private/qcoreapplication_p.h>
 #include <private/qcore_unix_p.h>
 #include "qdebug.h"
+#include "qloggingcategory.h"
 #include "qthreadstorage.h"
 #include <private/qtools_p.h>
 
@@ -404,7 +405,6 @@ void QThreadPrivate::finish()
         d->threadState = QThreadPrivate::Finishing;
         locker.unlock();
         emit thr->finished(QThread::QPrivateSignal());
-        qCDebug(lcDeleteLater) << "Sending deferred delete events as part of finishing thread" << thr;
         QCoreApplication::sendPostedEvents(nullptr, QEvent::DeferredDelete);
 
         void *data = &d->data->tls;

src/corelib/thread/qthread_win.cpp

@@ -230,7 +230,6 @@ void QThreadPrivate::finish(bool lockAnyway) noexcept
     if (lockAnyway)
         locker.unlock();
     emit thr->finished(QThread::QPrivateSignal());
-    qCDebug(lcDeleteLater) << "Sending deferred delete events as part of finishing thread" << thr;
     QCoreApplicationPrivate::sendPostedEvents(nullptr, QEvent::DeferredDelete, d->data);
     QThreadStorageData::finish(tls_data);
     if (lockAnyway)