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To:	cygwin AT cygwin DOT com
Subject:	Re: How to debug mintty or screen freeze
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From:	ht AT inf DOT ed DOT ac DOT uk (Henry S. Thompson)
Date:	Mon, 15 Nov 2010 10:25:24 +0000
In-Reply-To:	<AANLkTi=TE=T6ESQvkZOQRC8ue2cH9ZU7PbJaC5fpJD-m@mail.gmail.com> (Andy Koppe's message of "Mon, 8 Nov 2010 12:36:29 +0000")
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Andy Koppe writes:

> On 8 November 2010 10:15, Henry S. Thompson wrote:
>> Bear with me please, this is moderately complex:
>>
>> . . .the whole thing freezes solid.
>>
>> screen doesn't respond to escape commands, ~. does nothing, Control-C
>> has no effect, trying to close the window results in the "process not
>> responding" popup.
>>
>> It's not repeatable, in that reconnecting and changing to the same
>> gnus Subject buffer will succeed.
>>
>> I _presume_ some obscure character code is responsible. . .
>>
>> Two questions:
>>
>>  1) Anyone else seen anything like this?
>
> Not as such, but it could be to do with the following issue: if you
> cat a big file and press any key that sends a character, the terminal
> and cat will be deadlocked, like so:
>
> $ ps
> O    2408       1    2408       2408    ? 99498 12:27:13 /usr/bin/mintty
> O    2672    2772    2672       1580    5 99498 12:27:19 /usr/bin/cat
>
> They're both in write(), waiting for each other to read data from
> their side of the pty. Happens with all the pty-based terminals.
> Killing the cat resolves the deadlock, and the terminal merrily
> continues.

OK, that's not it -- the ps output is

     5712       1    5712       5712    ? 1003 16:09:26 /c/Cygwin/bin/mintty
     5748    5712    5748       5768    1 1003 16:09:26 /usr/bin/screen
     6036    5748    6036       6036    ? 1003 16:09:27 /usr/bin/screen

and procexp shows mintty at 50% of the CPU, i.e. 100% of one of them.

Attaching with gdb shows

  #0  0x7c90120f in ntdll!DbgUiConnectToDbg () from  /c/WINDOWS/system32/ntdll.dll
  #1  0x7c951e40 in ntdll!KiIntSystemCall () from  /c/WINDOWS/system32/ntdll.dll
  #2  0x00000005 in ?? ()
  #3  0x00000004 in ?? ()
  #4  0x00000001 in ?? ()
  #5  0x19c3ffd0 in ?? ()
  #6  0xba338548 in ?? ()
  #7  0xffffffff in ?? ()
  #8  0x7c90e920 in strchr () from /c/WINDOWS/system32/ntdll.dll
  #9  0x7c951e60 in ntdll!KiIntSystemCall () from  /c/WINDOWS/system32/ntdll.dll
  #10 0x00000000 in ?? ()

in thread 6 and

  #0  0x6110b348 in memcpy () from /c/Cygwin/bin/cygwin1.dll
  #1  0x610f393a in dlrealloc () from /c/Cygwin/bin/cygwin1.dll
  #2  0x58ca0008 in ?? ()
  #3  0x698f0008 in ?? ()
  #4  0x082fffe8 in ?? ()
  #5  0x00000002 in ?? ()
  #6  0x0023c5bc in ?? ()
  #7  0x0000fffd in ?? ()
  #8  0x698f0008 in ?? ()
  #9  0x00506528 in ?? ()
  #10 0x08300000 in ?? ()
  #11 0x698f0008 in ?? ()
  #12 0x0023c8d0 in ?? ()
  #13 0x61071218 in realloc () from /c/Cygwin/bin/cygwin1.dll
  #14 0x0000fffd in ?? ()
  #15 0x005062a0 in ?? ()
  #16 0x0000000e in ?? ()
  #17 0x00000009 in ?? ()
  #18 0x0000000f in ?? ()
  #19 0x005062a8 in ?? ()
  #20 0x0023c8d0 in ?? ()
  #21 0x00020500 in ?? ()
  #22 0x00506528 in ?? ()
  #23 0x0000000f in ?? ()
  #24 0x005062a8 in ?? ()
  #25 0x610c01a5 in _sigfe () from /c/Cygwin/bin/cygwin1.dll
  #26 0x7475f1a6 in TF_InvalidAssemblyListCache () from /c/WINDOWS/system32/MSCTF.dll
  Cannot access memory at address 0x82fffec

in thread 1

I expect those are no use.

Should I try building a with-symbols version from source?

ht
-- 
       Henry S. Thompson, School of Informatics, University of Edinburgh
      10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440
                Fax: (44) 131 651-1426, e-mail: ht AT inf DOT ed DOT ac DOT uk
                       URL: http://www.ltg.ed.ac.uk/~ht/
 [mail from me _always_ has a .sig like this -- mail without it is forged spam]

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