Date: Tue, 9 Sep 2008 11:09:34 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: John Baldwin <jhb@FreeBSD.org> Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/kern subr_turnstile.c Message-ID: <alpine.BSF.1.10.0809091108100.66707@fledge.watson.org> In-Reply-To: <200809082140.m88LeNJW085481@repoman.freebsd.org> References: <200809082140.m88LeNJW085481@repoman.freebsd.org>
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On Mon, 8 Sep 2008, John Baldwin wrote: > SVN rev 182879 on 2008-09-08 21:40:15Z by jhb > > - Reduce scope of #ifdef's in uma_zcreate() call in init_turnstile0(). > - Set UMA_ZONE_NOFREE so that the per-turnstile spin locks are type stable > to avoid a race where one thread might dereference a lock in a free'd > turnstile that was previously used by another thread. Is this a feature or a workaround for a bug? Normally in the above scenario we would consider use-after-free a bug or symptom of a larger architectural problem rather than a feature. At least, that's what I consider similar use of UMA_ZONE_NOFREE where it persists in the network stack :-). Robert N M Watson Computer Laboratory University of Cambridge
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