Re: segfaults building documentation when machine under load

I compiled with thread sanitizer. It gives a lot of warnings just for
starting/stopping octave. If I run
TSAN_OPTIONS=second_deadlock_stack=1 ./run-octave --norc --silent
--no-history --eval 'figure (1, "visible", "off");' 2>tsan_plot.txt

A warnings that stands out is:
WARNING: ThreadSanitizer: data race (pid=24895)
  Atomic write of size 8 at 0x7b0800000e80 by main thread (mutexes: write
M103436625102881360):
    #0 __tsan_atomic64_fetch_add <null> (libtsan.so.0+0x6987d)
    #1 octave_atomic_increment ../liboctave/util/oct-atomic.c:41
(liboctave.so.8+0xd66884)
    #2 dim_vector::increment_count() ../liboctave/array/dim-vector.h:104
(liboctgui.so.6+0x20da84)
    #3 dim_vector::dim_vector() ../liboctave/array/dim-vector.h:271
(liboctgui.so.6+0x20dbe3)
    #4 Array<double>::Array() ../liboctave/array/Array.h:257
(liboctgui.so.6+0x20fe59)
    #5 MArray<double>::MArray() ../liboctave/array/MArray.h:72
(liboctgui.so.6+0x20f640)
    #6 NDArray::NDArray() <null> (liboctgui.so.6+0x20e142)
    #7 Matrix::Matrix() ../liboctave/array/dMatrix.h:62
(liboctgui.so.6+0x20e31e)
    #8 QtHandles::Figure::Figure(octave::base_qobject&,
octave::interpreter&, graphics_object const&, QtHandles::FigureWindow*)
../libgui/graphics/Figure.cc:137 (liboctgui.so.6+0x2305dd)
    #9 QtHandles::Figure::create(octave::base_qobject&,
octave::interpreter&, graphics_object const&)
../libgui/graphics/Figure.cc:116 (liboctgui.so.6+0x230155)
    #10 QtHandles::qt_graphics_toolkit::create_object(double)
../libgui/graphics/qt-graphics-toolkit.cc:405 (liboctgui.so.6+0x28ee58)
    #11 QtHandles::qt_graphics_toolkit::qt_static_metacall(QObject*,
QMetaObject::Call, int, void**)
libgui/graphics/moc-qt-graphics-toolkit.cc:122 (liboctgui.so.6+0x29a2c4)
    #12 QObject::event(QEvent*) <null> (libQt5Core.so.5+0x27c935)
    #13 QCoreApplication::notifyInternal2(QObject*, QEvent*) <null>
(libQt5Core.so.5+0x252ec5)
    #14 octave::qt_application::execute()
../libgui/src/qt-application.cc:73 (liboctgui.so.6+0x366cb1)
    #15 main ../src/main-gui.cc:106 (lt-octave-gui+0x401c32)

  Previous read of size 8 at 0x7b0800000e80 by thread T6:
    #0 octave_atomic_increment ../liboctave/util/oct-atomic.c:43
(liboctave.so.8+0xd66890)
    #1 dim_vector::increment_count() ../liboctave/array/dim-vector.h:104
(liboctgui.so.6+0x20da84)
    #2 dim_vector::dim_vector() ../liboctave/array/dim-vector.h:271
(liboctgui.so.6+0x20dbe3)

<...>

the full tsan_plot.txt is attached.

Dmitri.
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