Bug#954197: GFileMonitor can deadlock if not cancelled before last unref

[Simon McVittie]

Control: retitle -1 GFileMonitor can deadlock if not cancelled before last unref
Control: severity -1 normal

On Wed, 18 Mar 2020 at 09:37:15 +0000, Simon McVittie wrote:
> Looks like <https://gitlab.gnome.org/GNOME/glib/issues/1941>. The
> workaround, which gegl might be able to use, is to always cancel
> file monitors before their last-unref is reached.

I have done that in gegl and it seems to have resolved the FTBFS.

According to GLib developers, best-practice is to cancel file monitors,
close files and sockets, etc. before their last-unref *anyway*, similar
to the advice given for file-like objects in modern Python: this avoids
doing complicated things in the dispose() and finalize() callbacks,
and avoids leaking resources if a reference cycle, a temporary ref
taken while delivering events or a ref taken by a worker thread keeps
the object alive. So this workaround is not just a workaround, it is
also an improvement to gegl.

    smcv