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@ -0,0 +1,110 @@ |
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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()); |