Why would a kill -2 not work?

Chuck Swiger cswiger at mac.com
Mon May 18 18:24:40 UTC 2009


On May 18, 2009, at 9:23 AM, Peter Steele wrote:
> Under what circumstances might a "kill -2 nnn" not work. I have a  
> Python app with a signal handler configured to catch INT signals. It  
> seems to work fine, but we've recently noticed that after the app  
> has run for a while the kill -2 no longer works. This seems pretty  
> suspicious, perhaps indicating our app is misbehaving in some way.  
> What might cause the signal handler to stop working?

The main reason might be that your process is already in another  
signal handler or is otherwise blocked in a system call and won't get  
the new signal until it completes the current situation.

The amount of stuff you're allowed to do safely in a signal handler is  
pretty minimal-- you're better off setting a flag, returning from the  
signal handler, and having the next run past the main event loop or  
whatever check for the flag and handle things in a normal app  
context.  If you try to do anything involving malloc() or s/printf,  
etc, you're running risks.  "man sigaction" is likely to be  


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