From 49df01ca70781851c941fdabfc997464b2c05fb0 Mon Sep 17 00:00:00 2001 From: Miao Wang Date: Thu, 22 Jan 2026 01:30:17 +0800 Subject: [PATCH] [PATCH] Revert "QProcessEnvironment: simplify locking" This reverts commit c5d6b263c204cb09db2be36826e19acb03dc24fb. The commit being reverted assumes the mutex is only protecting 'nameMap' and nothing else is mutable, which is false. The mutex is not only protecting 'nameMap' but also protecting the containing value objects, since even though the value object is accessed read-only, its implementation mutates its internal states for 2-way conversion between ByteArray and QString. Commit 85e61297f7b02297641826332dbdbc845a88c34b ("restore QProcessEnvironment shared data thread safety on unix") said that implicit sharing together with 'mutable' is a time bomb and the bomb is triggered by the reverted commit. Fixes: QTBUG-142938 Pick-to: 6.11 6.10 6.8 Change-Id: I9e3234f0eb2c691eccf753a11f63fae9944bd503 Reviewed-by: Thiago Macieira Reviewed-by: Oswald Buddenhagen Gbp-Pq: Name upstream_revert_simplify_locking.diff --- src/corelib/io/qprocess.cpp | 12 ++++++-- src/corelib/io/qprocess_p.h | 50 ++++++++++++++++++-------------- src/corelib/io/qprocess_unix.cpp | 2 ++ 3 files changed, 40 insertions(+), 24 deletions(-) diff --git a/src/corelib/io/qprocess.cpp b/src/corelib/io/qprocess.cpp index e03fc3dfe..4a30bb7c9 100644 --- a/src/corelib/io/qprocess.cpp +++ b/src/corelib/io/qprocess.cpp @@ -105,7 +105,6 @@ void QProcessEnvironmentPrivate::insert(const QProcessEnvironmentPrivate &other) vars.insert(it.key(), it.value()); #ifdef Q_OS_UNIX - const OrderedNameMapMutexLocker locker(this, &other); auto nit = other.nameMap.constBegin(); const auto nend = other.nameMap.constEnd(); for ( ; nit != nend; ++nit) @@ -206,8 +205,10 @@ bool comparesEqual(const QProcessEnvironment &lhs, const QProcessEnvironment &rh { if (lhs.d == rhs.d) return true; - - return lhs.d && rhs.d && lhs.d->vars == rhs.d->vars; + if (!(lhs.d && rhs.d)) + return false; + QProcessEnvironmentPrivate::OrderedMutexLocker locker(lhs.d, rhs.d); + return lhs.d->vars == rhs.d->vars; } /*! @@ -265,6 +266,7 @@ bool QProcessEnvironment::contains(const QString &name) const { if (!d) return false; + QProcessEnvironmentPrivate::MutexLocker locker(d); return d->vars.contains(d->prepareName(name)); } @@ -315,6 +317,7 @@ QString QProcessEnvironment::value(const QString &name, const QString &defaultVa if (!d) return defaultValue; + QProcessEnvironmentPrivate::MutexLocker locker(d); const auto it = d->vars.constFind(d->prepareName(name)); if (it == d->vars.constEnd()) return defaultValue; @@ -339,6 +342,7 @@ QStringList QProcessEnvironment::toStringList() const { if (!d) return QStringList(); + QProcessEnvironmentPrivate::MutexLocker locker(d); return d->toList(); } @@ -355,6 +359,7 @@ QStringList QProcessEnvironment::keys() const { if (!d) return QStringList(); + QProcessEnvironmentPrivate::MutexLocker locker(d); return d->keys(); } @@ -371,6 +376,7 @@ void QProcessEnvironment::insert(const QProcessEnvironment &e) return; // our re-impl of detach() detaches from null + QProcessEnvironmentPrivate::MutexLocker locker(e.d); d->insert(*e.d); } diff --git a/src/corelib/io/qprocess_p.h b/src/corelib/io/qprocess_p.h index 9510101e7..cb86968b7 100644 --- a/src/corelib/io/qprocess_p.h +++ b/src/corelib/io/qprocess_p.h @@ -110,22 +110,16 @@ public: inline QString nameToString(const Key &name) const { return name; } inline Value prepareValue(const QString &value) const { return value; } inline QString valueToString(const Value &value) const { return value; } -#else - struct NameMapMutexLocker : public QMutexLocker - { - NameMapMutexLocker(const QProcessEnvironmentPrivate *d) : QMutexLocker(&d->nameMapMutex) {} + struct MutexLocker { + MutexLocker(const QProcessEnvironmentPrivate *) {} }; - struct OrderedNameMapMutexLocker : public QOrderedMutexLocker - { - OrderedNameMapMutexLocker(const QProcessEnvironmentPrivate *d1, - const QProcessEnvironmentPrivate *d2) - : QOrderedMutexLocker(&d1->nameMapMutex, &d2->nameMapMutex) - {} + struct OrderedMutexLocker { + OrderedMutexLocker(const QProcessEnvironmentPrivate *, + const QProcessEnvironmentPrivate *) {} }; - +#else inline Key prepareName(const QString &name) const { - const NameMapMutexLocker locker(this); Key &ent = nameMap[name]; if (ent.isEmpty()) ent = name.toLocal8Bit(); @@ -134,27 +128,40 @@ public: inline QString nameToString(const Key &name) const { const QString sname = QString::fromLocal8Bit(name); - { - const NameMapMutexLocker locker(this); - nameMap[sname] = name; - } + nameMap[sname] = name; return sname; } inline Value prepareValue(const QString &value) const { return Value(value); } inline QString valueToString(const Value &value) const { return value.string(); } + struct MutexLocker : public QMutexLocker + { + MutexLocker(const QProcessEnvironmentPrivate *d) : QMutexLocker(&d->mutex) {} + }; + struct OrderedMutexLocker : public QOrderedMutexLocker + { + OrderedMutexLocker(const QProcessEnvironmentPrivate *d1, + const QProcessEnvironmentPrivate *d2) : + QOrderedMutexLocker(&d1->mutex, &d2->mutex) + {} + }; + QProcessEnvironmentPrivate() : QSharedData() {} QProcessEnvironmentPrivate(const QProcessEnvironmentPrivate &other) : - QSharedData(), vars(other.vars) + QSharedData() { + // This being locked ensures that the functions that only assign + // d pointers don't need explicit locking. // We don't need to lock our own mutex, as this object is new and // consequently not shared. For the same reason, non-const methods // do not need a lock, as they detach objects (however, we need to // ensure that they really detach before using prepareName()). - NameMapMutexLocker locker(&other); + MutexLocker locker(&other); + vars = other.vars; nameMap = other.nameMap; - // We need to detach our nameMap, so that our mutex can protect it. - // As we are being detached, it likely would be detached a moment later anyway. + // We need to detach our members, so that our mutex can protect them. + // As we are being detached, they likely would be detached a moment later anyway. + vars.detach(); nameMap.detach(); } #endif @@ -165,7 +172,8 @@ public: #ifdef Q_OS_UNIX typedef QHash NameHash; mutable NameHash nameMap; - mutable QMutex nameMapMutex; + + mutable QMutex mutex; #endif static QProcessEnvironment fromList(const QStringList &list); diff --git a/src/corelib/io/qprocess_unix.cpp b/src/corelib/io/qprocess_unix.cpp index d9b672df1..e269bddad 100644 --- a/src/corelib/io/qprocess_unix.cpp +++ b/src/corelib/io/qprocess_unix.cpp @@ -398,6 +398,8 @@ QChildProcess::CharPointerList::CharPointerList(const QProcessEnvironmentPrivate if (!environment) return; + QProcessEnvironmentPrivate::MutexLocker locker(environment); + const QProcessEnvironmentPrivate::Map &env = environment->vars; qsizetype count = env.size(); pointers.reset(new char *[count + 1]); -- 2.30.2