diff options
author | MÃ¥rten Nordheim <marten.nordheim@qt.io> | 2019-08-16 15:49:42 +0200 |
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committer | Volker Hilsheimer <volker.hilsheimer@qt.io> | 2019-08-19 07:27:45 +0000 |
commit | e9eddfd85628f0ec672895652c67443caa160b7b (patch) | |
tree | fcbfb6cd0205a07a82feff0f4e028a853e605d3d /src | |
parent | 77160d29234fe9ea570a515f32f53f864c947e4d (diff) |
Fix rare double-free in QObject machinery
As exposed by tst_QObjectRace::destroyRace we would sometimes end up
with a double-free when destroying a QSlotObject in multi-threaded
scenarios. One free would be done in ~QObject as the receiver was being
destroyed while the other free was done when deleting a QMetaCallEvent
object after we realized it was not needed because the receiver was
destroyed.
Since we can be in a separate thread from the receiver we should lock
before referencing the connection object.
Amends b7d073e9905bf9812ba96cecdcf6871a95517d30.
Change-Id: Icb53862dc880ae9a4e5581a1a9ee693573f7d9c7
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Diffstat (limited to 'src')
-rw-r--r-- | src/corelib/kernel/qobject.cpp | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp index 82fe546715..4a26e9cdc0 100644 --- a/src/corelib/kernel/qobject.cpp +++ b/src/corelib/kernel/qobject.cpp @@ -3728,6 +3728,15 @@ static void queued_activate(QObject *sender, int signal, QObjectPrivate::Connect while (argumentTypes[nargs-1]) ++nargs; + QBasicMutexLocker locker(signalSlotLock(c->receiver.loadRelaxed())); + if (!c->receiver.loadRelaxed()) { + // the connection has been disconnected before we got the lock + return; + } + if (c->isSlotObject) + c->slotObj->ref(); + locker.unlock(); + QMetaCallEvent *ev = c->isSlotObject ? new QMetaCallEvent(c->slotObj, sender, signal, nargs) : new QMetaCallEvent(c->method_offset, c->method_relative, c->callFunction, sender, signal, nargs); @@ -3746,9 +3755,11 @@ static void queued_activate(QObject *sender, int signal, QObjectPrivate::Connect args[n] = QMetaType::create(types[n], argv[n]); } - QBasicMutexLocker locker(signalSlotLock(c->receiver.loadRelaxed())); + locker.relock(); + if (c->isSlotObject) + c->slotObj->destroyIfLastRef(); if (!c->receiver.loadRelaxed()) { - // the connection has been disconnected before we got the lock + // the connection has been disconnected while we were unlocked locker.unlock(); delete ev; return; |