Fixes <https://bugs.gnu.org/42476>. Reported by linka on #guix. * gnu/packages/patches/qtbase-fix-krita-deadlock.patch: New file. * gnu/local.mk (dist_patch_DATA): Add it. * gnu/packages/qt.scm (qtbase-for-krita): New variable. * gnu/packages/kde.scm (krita)[inputs]: Replace qtbase with qtbase-for-krita.
		
			
				
	
	
		
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			110 lines
		
	
	
	
		
			3.6 KiB
		
	
	
	
		
			Diff
		
	
	
	
	
	
Fix a deadlock in Krita:
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https://bugreports.qt.io/browse/QTBUG-83207
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Patch copied from Qt bug tracker:
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https://codereview.qt-project.org/c/qt/qtbase/+/296034
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From 276fa8383a7535765be7182883ef4aade17ce013 Mon Sep 17 00:00:00 2001
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From: Thiago Macieira <thiago.macieira@intel.com>
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Date: Thu, 02 Apr 2020 12:08:41 -0300
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Subject: [PATCH] QLibrary: fix deadlock caused by fix to QTBUG-39642
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Commit ae6f73e8566fa76470937aca737141183929a5ec inserted a mutex around
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the entire load_sys(). We had reasoed that deadlocks would only occur if
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the object creation in instance() recursed into its own instance(),
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which was already a bug. But we had forgotten that dlopen()/
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LoadLibrary() executes initialization code from the module being loaded,
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which could cause a recursion back into the same QPluginLoader or
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QLibrary object. This recursion is benign because the module *is* loaded
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and dlopen()/LoadLibrary() returns the same handle.
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[ChangeLog][QtCore][QLibrary and QPluginLoader] Fixed a deadlock that
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would happen if the plugin or library being loaded has load-time
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initialization code (C++ global variables) that recursed back into the
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same QLibrary or QPluginLoader object.
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PS: QLibraryPrivate::loadPlugin() updates pluginState outside a mutex
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lock, so pluginState should be made an atomic variable. Once that is
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done, we'll only need locking the mutex to update errorString (no
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locking before loading).
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Fixes: QTBUG-83207
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Task-number: QTBUG-39642
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Change-Id: Ibdc95e9af7bd456a94ecfffd160209304e5ab2eb
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Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
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Reviewed-by: David Faure <david.faure@kdab.com>
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---
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diff --git a/src/corelib/plugin/qlibrary.cpp b/src/corelib/plugin/qlibrary.cpp
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index ddb053c..be9d92b 100644
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--- a/src/corelib/plugin/qlibrary.cpp
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+++ b/src/corelib/plugin/qlibrary.cpp
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@@ -576,9 +576,7 @@
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     Q_TRACE(QLibraryPrivate_load_entry, fileName);
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-    mutex.lock();
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     bool ret = load_sys();
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-    mutex.unlock();
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     if (qt_debug_component()) {
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         if (ret) {
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             qDebug() << "loaded library" << fileName;
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diff --git a/src/corelib/plugin/qlibrary_unix.cpp b/src/corelib/plugin/qlibrary_unix.cpp
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index 017aa97..a5c72f8 100644
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--- a/src/corelib/plugin/qlibrary_unix.cpp
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+++ b/src/corelib/plugin/qlibrary_unix.cpp
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@@ -123,6 +123,7 @@
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 bool QLibraryPrivate::load_sys()
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 {
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+    QMutexLocker locker(&mutex);
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     QString attempt;
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     QFileSystemEntry fsEntry(fileName);
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@@ -213,6 +214,7 @@
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     }
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 #endif
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+    locker.unlock();
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     bool retry = true;
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     Handle hnd = nullptr;
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     for (int prefix = 0; retry && !hnd && prefix < prefixes.size(); prefix++) {
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@@ -273,6 +275,8 @@
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         }
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     }
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 #endif
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+
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+    locker.relock();
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     if (!hnd) {
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         errorString = QLibrary::tr("Cannot load library %1: %2").arg(fileName, qdlerror());
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     }
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diff --git a/src/corelib/plugin/qlibrary_win.cpp b/src/corelib/plugin/qlibrary_win.cpp
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index 000bf76..ef58724 100644
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--- a/src/corelib/plugin/qlibrary_win.cpp
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+++ b/src/corelib/plugin/qlibrary_win.cpp
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@@ -78,6 +78,7 @@
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     //     fileName
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     //
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     // NB If it's a plugin we do not ever try the ".dll" extension
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+    QMutexLocker locker(&mutex);
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     QStringList attempts;
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     if (pluginState != IsAPlugin)
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@@ -95,6 +96,7 @@
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         attempts.prepend(QDir::rootPath() + fileName);
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 #endif
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+    locker.unlock();
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     Handle hnd = nullptr;
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     for (const QString &attempt : qAsConst(attempts)) {
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 #ifndef Q_OS_WINRT
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@@ -115,6 +117,7 @@
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 #ifndef Q_OS_WINRT
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     SetErrorMode(oldmode);
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 #endif
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+    locker.relock();
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     if (!hnd) {
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         errorString = QLibrary::tr("Cannot load library %1: %2").arg(
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                     QDir::toNativeSeparators(fileName), qt_error_string());
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