Hang in "double/triple" select()

[storm@cua.dk (Kim F. Storm)]

I happened to be using a "slightly old" version of CVS Emacs 

GNU Emacs 22.0.50.3 (i686-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
of 2006-01-19 on kfs-l.imdomain.dk

and went away from the screen for an hours so, and when I returned,
Emacs was stuck in a non-responsive mode with a "blank" emacs frame.

I attached to it with GDB, and this is what I got:

bt
#0  0x403d8122 in select () from /lib/libc.so.6
#1  0x402bbdc4 in _XlcPublicMethods () from /usr/X11R6/lib/libX11.so.6
#2  0x40210ee8 in _XFlush () from /usr/X11R6/lib/libX11.so.6
#3  0x402124fd in _XReply () from /usr/X11R6/lib/libX11.so.6
#4  0x401ff722 in XInternAtom () from /usr/X11R6/lib/libX11.so.6
#5  0x4066bf31 in _XimExtension ()
   from /usr/X11R6/lib/X11/locale/lib/common/ximcp.so.2
#6  0x4022e515 in XFilterEvent () from /usr/X11R6/lib/libX11.so.6
#7  0x080e59f5 in x_filter_event (dpyinfo=0x8621100, event=0xbfffd8a4)
    at xterm.c:5586
#8  0x080e7ad1 in XTread_socket (sd=0, expected=1, hold_quit=0xbfffe974)
    at xterm.c:7016
#9  0x0811a03b in read_avail_input (expected=1) at keyboard.c:6712
#10 0x0811a232 in handle_async_input () at keyboard.c:6858
#11 0x0811a275 in input_available_signal (signo=29) at keyboard.c:6900
#12 <signal handler called>
#13 0x403d8122 in select () from /lib/libc.so.6
#14 0x00000010 in ?? ()
#15 0x081164a6 in kbd_buffer_get_event (kbp=0xbffff0a0,
    used_mouse_menu=0xbffff39c) at keyboard.c:3935
#16 0x081148c5 in read_char (commandflag=1, nmaps=5, maps=0xbffff2a0,
    prev_event=137847801, used_mouse_menu=0xbffff39c) at keyboard.c:2862
#17 0x0811d41c in read_key_sequence (keybuf=0xbffff510, bufsize=30,
---Type <return> to continue, or q <return> to quit---
    prompt=137847801, dont_downcase_last=0, can_return_switch_frame=1,
    fix_current_buffer=1) at keyboard.c:8857
#18 0x0811197c in command_loop_1 () at keyboard.c:1531
#19 0x0818a7aa in internal_condition_case (bfun=0x811167b <command_loop_1>,
    handlers=137892113, hfun=0x81111c0 <cmd_error>) at eval.c:1467
#20 0x081114f3 in command_loop_2 () at keyboard.c:1323
#21 0x0818a228 in internal_catch (tag=137888369,
    func=0x81114d4 <command_loop_2>, arg=137847801) at eval.c:1213
#22 0x081114a6 in command_loop () at keyboard.c:1302
#23 0x08110f3f in recursive_edit_1 () at keyboard.c:995
#24 0x08111080 in Frecursive_edit () at keyboard.c:1056
#25 0x0810f97d in main (argc=1, argv=0xbffffb24) at emacs.c:1789
#26 0x40311917 in __libc_start_main () from /lib/libc.so.6
(gdb)


Unfortunately, the gdb process also hangs shortly after this
(I made the stupid mistake of trying to flush Emacs' display.)


#0  0x403d8122 in select () from /lib/libc.so.6
#1  0x402bbdc4 in _XlcPublicMethods () from /usr/X11R6/lib/libX11.so.6
#2  0x40210f02 in _XFlush () from /usr/X11R6/lib/libX11.so.6
#3  0x40210d19 in _XFlush () from /usr/X11R6/lib/libX11.so.6
#4  0x401f75ec in XFlush () from /usr/X11R6/lib/libX11.so.6
#5  0x080dda1e in x_flush (f=0x86a2e00) at xterm.c:389
#6  0x080dd9e7 in x_flush (f=0x0) at xterm.c:386
#7  <function called from gdb>
(gdb)


I'm not sure how to interpret this -- but given the recent reports of
problems with emacs hanging in select() this might be related.

The kernel is some RedHat 9 enterprise edition:

Linux 2.4.21-builder-1 #3 Tue Aug 12 13:37:02 CDT 2003 i686 i686 i386 GNU/Linux


-- 
Kim F. Storm <storm@cua.dk> http://www.cua.dk