110 lines
3.9 KiB
Diff
110 lines
3.9 KiB
Diff
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, 2 Apr 2020 12:08:41 -0300
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Subject: [PATCH 44/49] 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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src/corelib/plugin/qlibrary.cpp | 2 --
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src/corelib/plugin/qlibrary_unix.cpp | 4 ++++
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src/corelib/plugin/qlibrary_win.cpp | 3 +++
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3 files changed, 7 insertions(+), 2 deletions(-)
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diff --git a/src/corelib/plugin/qlibrary.cpp b/src/corelib/plugin/qlibrary.cpp
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index ddb053c26f..be9d92b204 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 @@ bool QLibraryPrivate::load()
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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 017aa97b66..a5c72f81d9 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 @@ QStringList QLibraryPrivate::prefixes_sys()
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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 @@ bool QLibraryPrivate::load_sys()
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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 @@ bool QLibraryPrivate::load_sys()
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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 000bf76276..ef58724be8 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 @@ bool QLibraryPrivate::load_sys()
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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 @@ bool QLibraryPrivate::load_sys()
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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 @@ bool QLibraryPrivate::load_sys()
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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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--
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2.25.2
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