From owner-cvs-all@FreeBSD.ORG  Fri Oct 28 15:45:36 2005
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From: John Baldwin <jhb@freebsd.org>
To: Stefan Farfeleder <stefanf@freebsd.org>
Date: Fri, 28 Oct 2005 10:33:46 -0400
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Cc: cvs-src@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org
Subject: Re: cvs commit: src/bin/sh memalloc.c memalloc.h miscbltin.c
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On Friday 28 October 2005 06:45 am, Stefan Farfeleder wrote:
> stefanf     2005-10-28 10:45:19 UTC
>
>   FreeBSD src repository
>
>   Modified files:
>     bin/sh               memalloc.c memalloc.h miscbltin.c
>   Log:
>   Protect malloc, realloc and free calls with INT{ON,OFF} directly in
> chkalloc, ckrealloc and ckfree (added), respectively.  sh jumps out of the
> signal handler using longjmp which is obviously a bad idea during malloc
> calls.
>
>   Note: I think there is still a small race here because volatile
> sig_atomic_t only guarantees atomic reads and writes while we're doing
> increments and decrements.
>
>   Protect a setmode call with INT{ON,OFF} as it calls malloc internally.
>
>   PR:             45478
>   Patch from:     Nate Eldredge

If you are just doing a simple reference count you can use an int and use 
either the refcount API from sys/refcount.h or the atomic_foo_int() 
operations directly from machine/atomic.h.  Those should all work fine in 
userland.

-- 
John Baldwin <jhb@FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org