[ARGUS] Re: Re: 2.0.6.fixes.1 core from improper signal handling

[slif at bellsouth.net]

My bad.  The death spiral begins at free(),
not a second calloc() as I described.
  [I guess i haven't had my second cup of coffee yet!]

Since calloc() and free() manage memory, I can imagine
that calloc() hadn't made the list tidy before
free() came along.

I think the proposed solution is still valid.
  [Set flag in ISR, check flag in loop]

I can imagine the flag should be checked before the
each opportunity to check for input.


-Mike


> 
> From: Carter Bullard <carter at qosient.com>
> Date: 2004/11/11 Thu AM 08:46:21 EST
> To: <slif at bellsouth.net>
> CC: Argus <argus-info at lists.andrew.cmu.edu>
> Subject: Re: 2.0.6.fixes.1 core from improper signal handling
> 
> Hmmmmm, just reacting without looking at the code, why
> is ArgusChildExit calling calloc()?
> Carter
> 
> 
> 
> 
> > From: <slif at bellsouth.net>
> > Date: Thu, 11 Nov 2004 8:44:09 -0500
> > To: <carter at qosient.com>
> > Cc: <argus-info at lists.andrew.cmu.edu>
> > Subject: 2.0.6.fixes.1 core from improper signal handling
> > 
> > Hi, Carter.
> > I've found an unusual occurrence that I doubt
> > can be recreated manually.  I think it can be prevented.
> > 
> > Problem:  One of the processes of the argus server
> > received a SIGCHLD signal during the processing of a
> > "C" library call, in this case "calloc".
> > 
> > The signal handler ArgusChildExit begins to cleanup the child,
> > as it is intended to do,
> > but dies terribly (SIGABRT) during another call to "calloc".
> > 
> > Apparently "calloc" is not intended to be called recursively
> >  :-)
> > 
> > Solution:
> > Create a new function ArgusScheduleChildExit that is wired to SIGCHLD.
> > It should set a program global flag, in a manner like ArgusUsr2Sig.
> > 
> > That flag can be used to conditionally call ArgusChildExit
> > from the top of the processing loop.
> >  [You know best which loops should include the call!]
> > 
> > This gives the software interrupt *caller* an opportunity to
> > finish its work, and return from interrupt.
> > 
> > 
> > Best Regards,
> > -Mike Slifcak
> > 
> 
> 
>