I can reproduce this on Arch Linux (kernel 4.1.2, Xorg ga8a0f64 and Mesa 8c8a71f0 from GIT) on Haswell, also using plasmashell:
#5  0x00007f5836872340 in brw_meta_fast_clear (brw=brw@entry=0x25f6ae8, fb=fb@entry=0x5555620, buffers=buffers@entry=34, partial_clear=partial_clear@entry=false) at brw_meta_fast_clear.c:451
#6  0x00007f583680f6cc in brw_clear (ctx=0x25f6ae8, mask=34) at brw_clear.c:247
#7  0x00007f5854d57946 in QSGBatchRenderer::Renderer::renderBatches() (this=this@entry=0x4d063e0) at scenegraph/coreapi/qsgbatchrenderer.cpp:2471
#8  0x00007f5854d5d536 in QSGBatchRenderer::Renderer::render() (this=<optimized out>) at scenegraph/coreapi/qsgbatchrenderer.cpp:2674
#9  0x00007f5854d6b0cf in QSGRenderer::renderScene(QSGBindable const&) (this=0x4d063e0, bindable=...) at scenegraph/coreapi/qsgrenderer.cpp:208
#10 0x00007f5854d6ba1b in QSGRenderer::renderScene(unsigned int) (this=<optimized out>, fboId=<optimized out>) at scenegraph/coreapi/qsgrenderer.cpp:168
#11 0x00007f5854d7f03e in QSGRenderContext::renderNextFrame(QSGRenderer*, unsigned int) (this=0x141c950, renderer=0x4d063e0, fboId=<optimized out>) at scenegraph/qsgcontext.cpp:558
#12 0x00007f5854dd12fb in QQuickWindowPrivate::renderSceneGraph(QSize const&) (this=this@entry=0x3e77470, size=...) at items/qquickwindow.cpp:383
#13 0x00007f5854d9daa1 in QSGGuiThreadRenderLoop::renderWindow(QQuickWindow*) (this=this@entry=0xbbefb0, window=0x3a3cfd0) at scenegraph/qsgrenderloop.cpp:375
#14 0x00007f5854d9ed41 in QSGGuiThreadRenderLoop::event(QEvent*) (this=0xbbefb0, e=<optimized out>) at scenegraph/qsgrenderloop.cpp:471
#15 0x00007f58527e4204 in QApplicationPrivate::notify_helper(QObject*, QEvent*) (this=this@entry=0x969130, receiver=receiver@entry=0xbbefb0, e=e@entry=0x7ffdbffd6c00) at kernel/qapplication.cpp:3717
#16 0x00007f58527e97e9 in QApplication::notify(QObject*, QEvent*) (this=0x7ffdbffd6fc0, receiver=0xbbefb0, e=0x7ffdbffd6c00) at kernel/qapplication.cpp:3500
#17 0x00007f585143431d in QCoreApplication::notifyInternal(QObject*, QEvent*) (this=0x7ffdbffd6fc0, receiver=0xbbefb0, event=event@entry=0x7ffdbffd6c00) at kernel/qcoreapplication.cpp:965
#18 0x00007f585148908a in QTimerInfoList::activateTimers() (event=0x7ffdbffd6c00, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:224
#19 0x00007f585148908a in QTimerInfoList::activateTimers() (this=0x9a0b80) at kernel/qtimerinfo_unix.cpp:637
#20 0x00007f5851489669 in idleTimerSourceDispatch(GSource*, GSourceFunc, gpointer) (source=<optimized out>) at kernel/qeventdispatcher_glib.cpp:177
#21 0x00007f5851489669 in idleTimerSourceDispatch(GSource*, GSourceFunc, gpointer) (source=<optimized out>) at kernel/qeventdispatcher_glib.cpp:224
#22 0x00007f584cdcfd57 in g_main_context_dispatch () at /usr/lib/libglib-2.0.so.0
#23 0x00007f584cdcffb0 in  () at /usr/lib/libglib-2.0.so.0
#24 0x00007f584cdd005c in g_main_context_iteration () at /usr/lib/libglib-2.0.so.0
#25 0x00007f5851489a3f in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x9a7040, flags=...) at kernel/qeventdispatcher_glib.cpp:418
#26 0x00007f5851432c5a in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=this@entry=0x7ffdbffd6e40, flags=..., flags@entry=...) at kernel/qeventloop.cpp:204
#27 0x00007f585143acfc in QCoreApplication::exec() () at kernel/qcoreapplication.cpp:1229
#28 0x000000000042ed66 in main ()