SSL warnings for WebDAV in debug mode

Imported from http://bugzilla.roxen.com/bugzilla/show_bug.cgi?id=6958

Reported by Jonas Wallden jonasw@roxen.com

I get frequent SSL warnings when accessing an EP WebDAV volume over HTTPS:

Internal server error: In callback mode in a different backend.
Stream is open
User callbacks: a=0 r=0 w=Stdio.Sendfile()->write_cb c=0
Internal callbacks: r=0 w=SSL.sslfile(Fd(131))->ssl_write_callback c=0
Backend: Pike.Backend(0)  This thread: Thread.Thread(4429115392)  Other thread: Thread.Thread(140735135998736)
Other thread backtrace:
-:1: Pike.Backend(0)->`()(3600.0)
----------
/Users/jonasw/hacks/Pike/pike/lib/modules/SSL.pmod/sslfile.pike (76a600ff):250: SSL.sslfile(Fd(131))->thread_error("In callback mode in a different backend.\n",Thread.Thread(140735135998736))
/Users/jonasw/hacks/Pike/pike/lib/modules/SSL.pmod/sslfile.pike (76a600ff):738: SSL.sslfile(Fd(131))->destroy()
packages/sitebuilder/modules/ac/pike-modules/AC.pmod (379eaf77):9082: AC_DB[1:2]->`->("passive_auth")
packages/sitebuilder/modules/ac/pike-modules/AC.pmod (379eaf77):6432: ModuleAC(RoxenModule(ep52/sitebuilder#0))->access_try("print-webdav",RequestID(/rep-webdav/feeds/photos/volvo-7.jpg),UNDEFINED)
modules/print/modules/rep-webdav.pike (818dd584):584: RoxenModule(ep52/rep-webdav#0)->authenticate("feeds/photos/volvo-7.jpg",@0=RequestID(/rep-webdav/feeds/photos/volvo-7.jpg))
modules/print/modules/rep-webdav.pike (818dd584):842: RoxenModule(ep52/rep-webdav#0)->handle_resource("feeds/photos/volvo-7.jpg",@0,0,1)
modules/print/modules/rep-webdav.pike (818dd584):756: RoxenModule(ep52/rep-webdav#0)->find_file("feeds/photos/volvo-7.jpg",@0)
base_server/configuration.pike (72099b9e):2263: Configuration(ep52)->low_get_file(@0,UNDEFINED)
base_server/configuration.pike (72099b9e):2521: Configuration(ep52)->get_file(@0,UNDEFINED,UNDEFINED)
base_server/configuration.pike (72099b9e):2496: Configuration(ep52)->handle_request(@0,UNDEFINED)
protocols/http.pike (60909d3c):3067: RequestID(/rep-webdav/feeds/photos/volvo-7.jpg)->handle_request()
protocols/http.pike (60909d3c):3010: RequestID(/rep-webdav/feeds/photos/volvo-7.jpg)->handle_request_from_queue()
base_server/roxen.pike (abfcfcaf):912: roxen()->handler_thread(3)

This is a fresh Roxen/5.4 with newly recompiled Pike 7.8.805. Is this due to the sslfile.pike disclaimer about false alarms or a real problem?

// FIXME: Looks like the following check can give false alarms since // an fd object can lose all refs even if some callbacks still are // registered.