Date: Thu, 16 Oct 2003 21:16:17 +1000 (EST) From: Bruce Evans <bde@zeta.org.au> To: Doug Rabson <dfr@FreeBSD.org> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/sys bus.h kobj.h param.h src/sys/kern subr_bus.c subr_kobj.c Message-ID: <20031016210328.T930@gamplex.bde.org> In-Reply-To: <200310160916.h9G9GSqQ067982@repoman.freebsd.org> References: <200310160916.h9G9GSqQ067982@repoman.freebsd.org>
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On Thu, 16 Oct 2003, Doug Rabson wrote: > dfr 2003/10/16 02:16:28 PDT > > FreeBSD src repository > > Modified files: > sys/sys bus.h kobj.h param.h > sys/kern subr_bus.c subr_kobj.c > Log: > * Add multiple inheritance to kobj. Each class can have zero or more base > ... > * Change the kobj method lookup algorithm to one which is SMP-safe. This > relies only on the constraint that an observer of a sequence of writes > of pointer-sized values will see exactly one of those values, not a > mixture of two or more values. This assumption holds for all processors > which FreeBSD supports. This assumption should be avoided by using atomic_load() (and atomic_store_mumble()). See a discussion of "atomicity of unlocked reads" last month. First implement atomic_load(). There is currently only atomic_load_acq_<type>(). "acq" gives acquire semantics which is more than what is needed here and our implementations may do more than what is required anyway for some arches. "<type>" is part of a bad API. Bruce
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