Ctrl-C not working as well as on Linux

Ctrl-C not working as well as on Linux

[Alex Goldman]

On Linux, after I start a program that consumes 100% of CPU time, I
can usually terminate it just by typing Ctrl-C. This is very
convenient to me as a developer. However, using Cygwin in the same
situation, the shell becomes "bash (Not Responding)", and I have to
invoke the process manager and kill the process from there. Does
anyone know why this happens and what can be done about it?

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Re: Ctrl-C not working as well as on Linux

[Eric Blake]

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According to Alex Goldman on 7/21/2005 2:49 AM:
> On Linux, after I start a program that consumes 100% of CPU time, I
> can usually terminate it just by typing Ctrl-C. This is very
> convenient to me as a developer. However, using Cygwin in the same
> situation, the shell becomes "bash (Not Responding)", and I have to
> invoke the process manager and kill the process from there. Does
> anyone know why this happens and what can be done about it?
> 

What terminal are you using?  If it is the Windows console, then you need
to have CYGWIN=tty in your environment before starting bash to ensure
saner behavior of Ctrl-C (at the expense of possibly breaking Windows
native applications in the same console).  See
http://cygwin.com/cygwin-ug-net/cygwin-ug-net.html#id4736242 or search
some recent threads on the issue.

Hint - following the problem reporting directions would have helped us
know right off whether you were using the Windows console:

> Problem reports:       http://cygwin.com/problems.html

- --
Life is short - so eat dessert first!

Eric Blake             ebb9@byu.net
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Re: Ctrl-C not working as well as on Linux

[Christopher Faylor]

On Thu, Jul 21, 2005 at 06:06:39AM -0600, Eric Blake wrote:
>According to Alex Goldman on 7/21/2005 2:49 AM:
>>On Linux, after I start a program that consumes 100% of CPU time, I can
>>usually terminate it just by typing Ctrl-C.  This is very convenient to
>>me as a developer.  However, using Cygwin in the same situation, the
>>shell becomes "bash (Not Responding)", and I have to invoke the process
>>manager and kill the process from there.  Does anyone know why this
>>happens and what can be done about it?
>
>What terminal are you using?  If it is the Windows console, then you
>need to have CYGWIN=tty in your environment before starting bash to
>ensure saner behavior of Ctrl-C (at the expense of possibly breaking
>Windows native applications in the same console).

?  CTRL-C should work just fine without CYGWIN=tty.  In fact, it should
work better than CYGWIN=tty in situations where system time is being
consumed by a runaway process.

I don't see any reason why either Cygwin or bash should become unresponsive
due to a program which consumes CPU.

>Hint - following the problem reporting directions would have helped us
>know right off whether you were using the Windows console:
>
>> Problem reports:       http://cygwin.com/problems.html

Right.  In this situation a test case and better description of the
problem is required, too.

cgf

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Re: Ctrl-C not working as well as on Linux

[Alex Goldman]

My tty settings are fine. I run Rxvt by calling 

C:
chdir C:\cygwin\bin
set CYGWIN=codepage:oem tty binmode title
rxvt -sl 1000 -e bash --login -i


Looking into this more closely, I noticed that the problem occurs for
programs compiled using the free MSVC++ Toolkit 2003, but not GCC.

I think you can reproduce this behavior, if you have this compiler
installed and configured:
compile the program below with

cl loop.c

and run it:

./loop.exe

I can not terminate it using Ctrl-C. I think this has something to do
with signal handling.

---- loop.c ----

int main() {
    for(;;);
    return 0;
}

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Re: Ctrl-C not working as well as on Linux

[Igor Pechtchanski]

On Thu, 21 Jul 2005, Alex Goldman wrote:

> On Linux, after I start a program that consumes 100% of CPU time, I
> can usually terminate it just by typing Ctrl-C. This is very
> convenient to me as a developer. However, using Cygwin in the same
> situation, the shell becomes "bash (Not Responding)", and I have to
> invoke the process manager and kill the process from there. Does
> anyone know why this happens and what can be done about it?

Must be a Windows (non-Cygwin) program.  Ctrl-C should still work, but it
would be interesting to strace the bash that invokes the program to see
what happens on Ctrl-C.

FYI, if you know the PID (cf "top"), you could use "/bin/kill -f WINPID"
to achieve the same effect as the task manager's "End process" button.
	Igor
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