Comment 15 for bug 232364

: ~; gdb -p 3045
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This GDB was configured as "i486-linux-gnu".
Attaching to process 3045
Reading symbols from /usr/bin/dbus-launch...Reading symbols from /usr/lib/debug/usr/bin/dbus-launch...done.
done.
Reading symbols from /usr/lib/libX11.so.6...done.
Loaded symbols for /usr/lib/libX11.so.6
Reading symbols from /lib/tls/i686/cmov/libc.so.6...done.
Loaded symbols for /lib/tls/i686/cmov/libc.so.6
Reading symbols from /usr/lib/libxcb-xlib.so.0...Reading symbols from /usr/lib/debug/usr/lib/libxcb-xlib.so.0.0.0...done.
done.
Loaded symbols for /usr/lib/libxcb-xlib.so.0
Reading symbols from /usr/lib/libxcb.so.1...Reading symbols from /usr/lib/debug/usr/lib/libxcb.so.1.0.0...done.
done.
Loaded symbols for /usr/lib/libxcb.so.1
Reading symbols from /lib/tls/i686/cmov/libdl.so.2...done.
Loaded symbols for /lib/tls/i686/cmov/libdl.so.2
Reading symbols from /lib/ld-linux.so.2...done.
Loaded symbols for /lib/ld-linux.so.2
Reading symbols from /usr/lib/libXau.so.6...done.
Loaded symbols for /usr/lib/libXau.so.6
Reading symbols from /usr/lib/libXdmcp.so.6...done.
Loaded symbols for /usr/lib/libXdmcp.so.6
Reading symbols from /lib/tls/i686/cmov/libnss_compat.so.2...done.
Loaded symbols for /lib/tls/i686/cmov/libnss_compat.so.2
Reading symbols from /lib/tls/i686/cmov/libnsl.so.1...done.
Loaded symbols for /lib/tls/i686/cmov/libnsl.so.1
Reading symbols from /lib/tls/i686/cmov/libnss_nis.so.2...done.
Loaded symbols for /lib/tls/i686/cmov/libnss_nis.so.2
Reading symbols from /lib/tls/i686/cmov/libnss_files.so.2...done.
Loaded symbols for /lib/tls/i686/cmov/libnss_files.so.2
0xb8002424 in __kernel_vsyscall ()
(gdb) bt
#0 0xb8002424 in __kernel_vsyscall ()
#1 0xb7e8484d in select () from /lib/tls/i686/cmov/libc.so.6
#2 0xb7da309a in _xcb_in_read_block (c=0x80579a8, buf=0x8057040, len=8)
    at xcb_in.c:248
#3 0xb7da2343 in xcb_connect_to_fd (fd=13, auth_info=0xbff1cdf0)
    at xcb_conn.c:133
#4 0xb7da4a51 in xcb_connect (displayname=0x0, screenp=0x0) at xcb_util.c:279
#5 0xb7f43717 in _XConnectXCB () from /usr/lib/libX11.so.6
#6 0xb7f2c029 in XOpenDisplay () from /usr/lib/libX11.so.6
#7 0x0804b3de in x11_init () at dbus-launch-x11.c:218
#8 0x0804abb2 in main (argc=5, argv=0xbff1d5a4) at dbus-launch.c:432
(gdb) quit
The program is running. Quit anyway (and detach it)? (y or n) EOF [assumed Y]
Detaching from program: /usr/bin/dbus-launch, process 3045

I tried replacing select in _xcb_in_read_block (actually read_block) with
poll and open the polling loop, like in the attached patch.
Now I cannot reproduce the problem at all (it was very hard, need
many reboots, before)

Just opening the loop turned out to be not enough.

Now, I don't understand what (in this case) seem to workaround
the issue when I use poll.