Date: Wed, 27 Mar 2002 13:48:33 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: Alfred Perlstein <bright@mu.org> Cc: jeff@freebsd.org, hackers@freebsd.org Subject: Re: uma and double free detection? Message-ID: <3CA23E31.CDAA9A78@mindspring.com> References: <20020327203236.GN93885@elvis.mu.org> <3CA239BB.A9A8F72A@mindspring.com> <20020327213247.GO93885@elvis.mu.org>
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Alfred Perlstein wrote: > * Terry Lambert <tlambert2@mindspring.com> [020327 13:30] wrote: > > Alfred Perlstein wrote: > > > > > > Can uma diagnose double free's? It doesn't seem to be able to > > > under a GENERIC config. :( > > > > THat's an INVARIANTS thing, even without UMA... > > /usr/src/sys/i386/conf % grep INVA BRIGHT > options INVARIANTS #Enable calls of extra sanity checking > options INVARIANT_SUPPORT #Extra sanity checks of internal structu > > All I got was a panic because uma seemed to get confused rather than > catch the double free. I got a similar untraceable panic because the ucred reference counter was overlayed with an invariants structure. Probably invariants is stomping something that is used as a marker into seeming validity. It's very tempting to require that invariants add their own crap to to the front of a structure, and then hide it, so that this is not possible. It was a real pain in the butt to track doewn the cred free problem. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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