Re: Intermittent failures with ctrl-c

[Tom Honermann <thonermann at coverity dot com>]

On 01/15/2013 09:04 PM, Christopher Faylor wrote:
> On Tue, Jan 15, 2013 at 05:16:57PM -0500, Tom Honermann wrote:
> > I noticed that some changes were checked in related to signal handling
> > and process termination recently, so I downloaded the most recent
> > snapshot (20130114) and tested again.  I was still able to produce
> > hanging processes (including hangs of strace.exe) by hitting ctrl-c in a
> > mintty window while Cygwin processes ran in an infinite loop inside of a
> > .bat file.  I was able to produce a hang ~1 out of 20 times.
>
> How does one run a .bat file inside mintty which handles CTRL-C?  AFAIK,
> a CTRL-C will just cause the .bat file to exit when run under bash.

Here is the test case:

1) Install the latest snapshot

2) Copy bash.exe, false.exe, and their dependent DLLs from a Cygwin 
install into the usr/bin directory of the snapshot.  For me this 
consisted of:
  bash.exe
  cygintl-8.dll
  cygiconv-2.dll
  cygreadline7.dll
  cygncurses-10.dll
  cygncursesw-10.dll
  cyggcc_s-1.dll
  false.exe

3) Create 'test.bat' in the usr/bin directory of the snapshot with the 
following contents:

@echo off
setlocal

set PATH=%CD%;%PATH%

:loop
echo test...
bash -c false
if not errorlevel 1 (
    echo exiting...
    exit /B 1
)
goto loop

4) Launch mintty using an existing Cygwin installation.  Naturally, this 
will run a shell from the existing Cygwin install.

5) Change directories to the usr/bin directory of the snapshot.

6) Start task manager or some other process monitoring tool and keep it 
running.  Run ./test.bat from the Cygwin shell running within mintty and 
interrupt it with ctrl-c.  Repeat until you see a new bash.exe or 
false.exe process persisting following the interrupt.  You'll likely 
have multiple bash processes running.  If you are able to reproduce, you 
should see one with a command line of 'bash -c false'.  Alternatively, 
if your process monitoring tool shows the path to the executable, you'll 
be able to identify it as the one from the usr/bin directory of the 
snapshot.

I rather doubt that the use of a .bat file is necessary to reproduce 
this hang, but I haven't tried producing a test case that doesn't use a 
.bat file.  This is a test case I was using when debugging the 
intermittent incorrect exit code issue.

Tom.


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