dev-qt/qtcore: QLibrary: fix deadlock caused by fix to QTBUG-39642

See also: https://bugreports.qt.io/browse/QTBUG-83207

Package-Manager: Portage-2.3.96, Repoman-2.3.22
Signed-off-by: Andreas Sturmlechner <[email protected]>

dev-qt/qtcore/files/qtcore-5.14.2-QLibrary-deadlock.patch

@@ -0,0 +1,106 @@
+From 276fa8383a7535765be7182883ef4aade17ce013 Mon Sep 17 00:00:00 2001
+From: Thiago Macieira <[email protected]>
+Date: Thu, 2 Apr 2020 12:08:41 -0300
+Subject: [PATCH] QLibrary: fix deadlock caused by fix to QTBUG-39642
+
+Commit ae6f73e8566fa76470937aca737141183929a5ec inserted a mutex around
+the entire load_sys(). We had reasoed that deadlocks would only occur if
+the object creation in instance() recursed into its own instance(),
+which was already a bug. But we had forgotten that dlopen()/
+LoadLibrary() executes initialization code from the module being loaded,
+which could cause a recursion back into the same QPluginLoader or
+QLibrary object. This recursion is benign because the module *is* loaded
+and dlopen()/LoadLibrary() returns the same handle.
+
+[ChangeLog][QtCore][QLibrary and QPluginLoader] Fixed a deadlock that
+would happen if the plugin or library being loaded has load-time
+initialization code (C++ global variables) that recursed back into the
+same QLibrary or QPluginLoader object.
+
+PS: QLibraryPrivate::loadPlugin() updates pluginState outside a mutex
+lock, so pluginState should be made an atomic variable. Once that is
+done, we'll only need locking the mutex to update errorString (no
+locking before loading).
+
+Fixes: QTBUG-83207
+Task-number: QTBUG-39642
+Change-Id: Ibdc95e9af7bd456a94ecfffd160209304e5ab2eb
+Reviewed-by: Volker Hilsheimer <[email protected]>
+Reviewed-by: David Faure <[email protected]>
+---
+ src/corelib/plugin/qlibrary.cpp      | 2 --
+ src/corelib/plugin/qlibrary_unix.cpp | 4 ++++
+ src/corelib/plugin/qlibrary_win.cpp  | 3 +++
+ 3 files changed, 7 insertions(+), 2 deletions(-)
+
+diff --git a/src/corelib/plugin/qlibrary.cpp b/src/corelib/plugin/qlibrary.cpp
+index ddb053c26fa..be9d92b2048 100644
+--- a/src/corelib/plugin/qlibrary.cpp
++++ b/src/corelib/plugin/qlibrary.cpp
+@@ -576,9 +576,7 @@ bool QLibraryPrivate::load()
+
+     Q_TRACE(QLibraryPrivate_load_entry, fileName);
+
+-    mutex.lock();
+     bool ret = load_sys();
+-    mutex.unlock();
+     if (qt_debug_component()) {
+         if (ret) {
+             qDebug() << "loaded library" << fileName;
+diff --git a/src/corelib/plugin/qlibrary_unix.cpp b/src/corelib/plugin/qlibrary_unix.cpp
+index 017aa97b66a..a5c72f81d96 100644
+--- a/src/corelib/plugin/qlibrary_unix.cpp
++++ b/src/corelib/plugin/qlibrary_unix.cpp
+@@ -123,6 +123,7 @@ QStringList QLibraryPrivate::prefixes_sys()
+
+ bool QLibraryPrivate::load_sys()
+ {
++    QMutexLocker locker(&mutex);
+     QString attempt;
+     QFileSystemEntry fsEntry(fileName);
+
+@@ -213,6 +214,7 @@ bool QLibraryPrivate::load_sys()
+     }
+ #endif
+
++    locker.unlock();
+     bool retry = true;
+     Handle hnd = nullptr;
+     for (int prefix = 0; retry && !hnd && prefix < prefixes.size(); prefix++) {
+@@ -273,6 +275,8 @@ bool QLibraryPrivate::load_sys()
+         }
+     }
+ #endif
++
++    locker.relock();
+     if (!hnd) {
+         errorString = QLibrary::tr("Cannot load library %1: %2").arg(fileName, qdlerror());
+     }
+diff --git a/src/corelib/plugin/qlibrary_win.cpp b/src/corelib/plugin/qlibrary_win.cpp
+index 000bf762763..ef58724be8e 100644
+--- a/src/corelib/plugin/qlibrary_win.cpp
++++ b/src/corelib/plugin/qlibrary_win.cpp
+@@ -78,6 +78,7 @@ bool QLibraryPrivate::load_sys()
+     //     fileName
+     //
+     // NB If it's a plugin we do not ever try the ".dll" extension
++    QMutexLocker locker(&mutex);
+     QStringList attempts;
+
+     if (pluginState != IsAPlugin)
+@@ -95,6 +96,7 @@ bool QLibraryPrivate::load_sys()
+         attempts.prepend(QDir::rootPath() + fileName);
+ #endif
+
++    locker.unlock();
+     Handle hnd = nullptr;
+     for (const QString &attempt : qAsConst(attempts)) {
+ #ifndef Q_OS_WINRT
+@@ -115,6 +117,7 @@ bool QLibraryPrivate::load_sys()
+ #ifndef Q_OS_WINRT
+     SetErrorMode(oldmode);
+ #endif
++    locker.relock();
+     if (!hnd) {
+         errorString = QLibrary::tr("Cannot load library %1: %2").arg(
+                     QDir::toNativeSeparators(fileName), qt_error_string());