(This appears to be caused by a recent update to Adobe Reader.)
We have a WinForms app that embeds an Adobe Reader through a WebBrowser
control (i.e., not by referencing the ActiveX DLL directly). When closing the last instance of that control, the entire app hangs for about 15 seconds.
I can "work around" this by not disposing the control; see also this related answer. But that hardly sounds like a safe solution.
During the hang,
- nothing of note happens in our user-level code, according to dotTrace
- nothing at all happens in the
AcroRd32
process, according to ProcMon. Literally zilch. There's lots of activity before the hang for a second or two, then nothing, then it starts again another almost exactly 15 seconds later.
I'm guessing this is some kind of lock with a timeout, but I don't really know how to track this down any further.