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Date: Sun, 03 Jun 2012 08:54:20 -0400
From: Ken Brown <kbrown AT cornell DOT edu>
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To: cygwin AT cygwin DOT com
Subject: Re: "emacs -nw" hangs in a terminal
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On 6/2/2012 11:08 PM, Christopher Faylor wrote:
> On Fri, May 25, 2012 at 04:07:32PM -0400, Ken Brown wrote:
>> On 5/25/2012 2:49 PM, Ken Brown wrote:
>>> On 5/25/2012 10:35 AM, Corinna Vinschen wrote:
>>>> I applied a patch which calls the signal handler after cleanup. The
>>>> downside is that the signal handler is only called if select is called
>>>> from the main thread. A better patch would perhaps be to stop all
>>>> threads, call the signal handler, and restart the threads afterwards,
>>>> but this is more tricky.
>>>
>>> Thanks! That fixes it. I appreciate all your work on this.
>>>
>>> I'm in the process now of testing to see if this also fixes an emacs
>>> crash I've been getting when I build emacs with GSettings support
>>> (http://cygwin.com/ml/cygwin-xfree/2012-04/msg00048.html).
>>
>> Here's what I'm now seeing with that build.  If I start emacs and do
>> 'M-x shell', emacs hangs (but doesn't crash).  Attaching gdb and doing a
>> backtrace of all threads, I see that cygwin_select has been called in
>> two threads other than the main one:
>>
>> Thread 8 (Thread 2784.0x19c):
>> #0  0x7702013d in ntdll!RtlEnableEarlyCriticalSectionEventCreation ()
>>     from /c/windows/SysWOW64/ntdll.dll
>> #1  0x7702013d in ntdll!RtlEnableEarlyCriticalSectionEventCreation ()
>>     from /c/windows/SysWOW64/ntdll.dll
>> #2  0x74fe0bdd in WaitForMultipleObjectsEx ()
>>     from /c/windows/syswow64/KERNELBASE.dll
>> #3  0x00000004 in ?? ()
>> #4  0x74ed1a2c in KERNEL32!GetVolumePathNamesForVolumeNameA ()
>>     from /c/windows/syswow64/kernel32.dll
>> #5  0xff11c868 in ?? ()
>> #6  0x74ed4208 in KERNEL32!CheckForReadOnlyResource ()
>>     from /c/windows/syswow64/kernel32.dll
>> #7  0x00000004 in ?? ()
>> #8  0x610d0b24 in select_stuff::wait (this=0xff11cba4, readfds=0xff11cb00,
>>      writefds=0xff11cae0, exceptfds=0xff11cac0, ms=4294967295)
>>      at
>> /ext/build/netrel/src/cygwin-snapshot-20120525-1/winsup/cygwin/select.cc:320
>> #9  0x610d154b in cygwin_select (maxfds=13, readfds=0xff11cc70,
>>      writefds=0xff11cc50, exceptfds=0xff11cc30, to=0x0)
>>      at
>> /ext/build/netrel/src/cygwin-snapshot-20120525-1/winsup/cygwin/select.cc:158
>> #10 0x610b2b5a in poll (fds=0x8012db00, nfds=3, timeout=-1)
>>      at
>> /ext/build/netrel/src/cygwin-snapshot-20120525-1/winsup/cygwin/poll.cc:87
>> #11 0x610d5575 in _sigfe () from /usr/bin/cygwin1.dll
>> #12 0xffffffff in ?? ()
>> #13 0x8012db00 in ?? ()
>> #14 0x6ac1e759 in g_main_loop_run () from /usr/bin/cygglib-2.0-0.dll
>> #15 0x6ad96d40 in g_dbus_proxy_call_with_unix_fd_list_sync ()
>>     from /usr/bin/cyggio-2.0-0.dll
>> #16 0x6ac401ef in g_thread_proxy () from /usr/bin/cygglib-2.0-0.dll
>> #17 0x610fca42 in pthread::thread_init_wrapper (arg=0x80130e00)
>>      at
>> /ext/build/netrel/src/cygwin-snapshot-20120525-1/winsup/cygwin/thread.cc:2104
>> #18 0x61086f62 in thread_wrapper (arg=0x0)
>>      at
>> /ext/build/netrel/src/cygwin-snapshot-20120525-1/winsup/cygwin/miscfuncs.cc:547
>> #19 0x00000000 in ?? ()
>>
>> Thread 7 (Thread 2784.0xb4c):
>> #0  0x7702013d in ntdll!RtlEnableEarlyCriticalSectionEventCreation ()
>>     from /c/windows/SysWOW64/ntdll.dll
>> #1  0x7702013d in ntdll!RtlEnableEarlyCriticalSectionEventCreation ()
>>     from /c/windows/SysWOW64/ntdll.dll
>> #2  0x74fe0bdd in WaitForMultipleObjectsEx ()
>>     from /c/windows/syswow64/KERNELBASE.dll
>> #3  0x00000003 in ?? ()
>> #4  0x74ed1a2c in KERNEL32!GetVolumePathNamesForVolumeNameA ()
>>     from /c/windows/syswow64/kernel32.dll
>> #5  0xff21c858 in ?? ()
>> #6  0x74ed4208 in KERNEL32!CheckForReadOnlyResource ()
>>     from /c/windows/syswow64/kernel32.dll
>> #7  0x00000003 in ?? ()
>> #8  0x610d0b24 in select_stuff::wait (this=0xff21cb94, readfds=0xff21caf0,
>>      writefds=0xff21cad0, exceptfds=0xff21cab0, ms=4294967295)
>>      at
>> /ext/build/netrel/src/cygwin-snapshot-20120525-1/winsup/cygwin/select.cc:320
>> #9  0x610d154b in cygwin_select (maxfds=8, readfds=0xff21cc60,
>>      writefds=0xff21cc40, exceptfds=0xff21cc20, to=0x0)
>>      at
>> /ext/build/netrel/src/cygwin-snapshot-20120525-1/winsup/cygwin/select.cc:158
>> #10 0x610b2b5a in poll (fds=0x8009b3c0, nfds=1, timeout=-1)
>>      at
>> /ext/build/netrel/src/cygwin-snapshot-20120525-1/winsup/cygwin/poll.cc:87
>> #11 0x610d5575 in _sigfe () from /usr/bin/cygwin1.dll
>> #12 0xffffffff in ?? ()
>> #13 0x8009b3c0 in ?? ()
>> #14 0x6ac1e759 in g_main_loop_run () from /usr/bin/cygglib-2.0-0.dll
>> #15 0x63e32eca in gvdb_table_walk ()
>>     from /usr/lib/gio/modules/cygdconfsettings.dll
>> #16 0x6ac401ef in g_thread_proxy () from /usr/bin/cygglib-2.0-0.dll
>> #17 0x610fca42 in pthread::thread_init_wrapper (arg=0x8009c700)
>>      at
>> /ext/build/netrel/src/cygwin-snapshot-20120525-1/winsup/cygwin/thread.cc:2104
>> #18 0x61086f62 in thread_wrapper (arg=0x0)
>>      at
>> /ext/build/netrel/src/cygwin-snapshot-20120525-1/winsup/cygwin/miscfuncs.cc:547
>> #19 0x00000000 in ?? ()
>>
>> It looks like these threads are being used by GLib, which is running a
>> loop that calls poll, which calls cygwin_select.  So maybe the "better
>> patch" that you referred to would fix this hang.
>
> Ken, can you confirm/deny that the changes that I just made to select()
> at least still work as well as Corinna's temporary (that's what the
> ChangeLog says at least) change above?  They are in the latest snapshot.

No, they don't.  There's no crash, but I'm seeing two problems in emacs 
and a problem with the X server.  My emacs tests were done with emacs-24 
in mintty on 64-bit Windows 7.  I wanted to test it under X also, but I 
couldn't because of the X server problem.

1. When I type into emacs, it's very slow to echo the keystrokes and 
respond.

2. When I start a shell under emacs (<Alt-X>shell<return>), the shell 
doesn't finish initializing.  It doesn't display a prompt, and it 
doesn't execute commands I type.

3. If I start the X server using the Start Menu shortcut, startxwin 
never finishes, and the xterm window doesn't display.  I have to kill 
startxwin from a terminal.

Ken

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