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Re: [BUG] Bash not reacting to Ctrl-C


From: Chet Ramey
Subject: Re: [BUG] Bash not reacting to Ctrl-C
Date: Tue, 08 Feb 2011 21:50:06 -0500
User-agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.13) Gecko/20101207 Lightning/1.0b2 Thunderbird/3.1.7

On 2/8/11 7:11 PM, Ingo Molnar wrote:
> 
> * Chet Ramey <address@hidden> wrote:
> 
>> On 2/8/11 4:17 PM, Oleg Nesterov wrote:
>>
>>> Once again. If bash gets ^C and at the same time the current foreground
>>> child exits normally (either because this jctl signal races with exit()
>>> or because the child hooks SIGINT and exits after that) SIGINT is lost.
>>>
>>> set_job_status_and_cleanup() insists that WTERMSIG(child->status) should
>>> be SIGINT, iow the child should be killed by the same signal. Otherwise
>>> it is not going to kill itself, and the next wait_for() clears
>>> wait_sigint_received.
>>>
>>> This all looks intentional, but this means ^C can never work reliably.
>>
>> It depends on what you mean by `reliably'.  Consider a script that runs
>> emacs, then does other processing when emacs completes.  Emacs uses SIGINT
>> internally to interrupt editing commands, but handles it and does not exit
>> as a result.  Since emacs is run from a script, and job control is not
>> enabled, the shell receives the SIGINT also, because it is in the
>> terminal's foreground process group.  Should the shell abort the script
>> when emacs exits?
> 
> Could you try the reproducer please?
> 
> Once you run it, try to stop it via Ctrl-C, and try to do this a couple of 
> times.
> 
> Do you consider it normal that it often takes 2-3 Ctrl-C attempts to 
> interrupt that 
> script, that it is not possible to stop the script reliably with a single 
> Ctrl-C?
> 
> This issue occurs all the time on different hardware and on different 
> distributions, 
> during make jobs and other simpler scripts, etc. - i just simplified it down 
> to a 
> simple testcase.
> 
> Oleg also found another simple testcase i think - and Thomas (Cc:-ed) 
> reported 
> similar Ctrl-C problems with Bash as well.

I tried to reproduce it and wasn't able to.  I use Mac OS X.

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/



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