Date: Tue, 19 Oct 2004 15:03:26 -0700 From: Julian Elischer <julian@elischer.org> To: John Baldwin <jhb@freebsd.org> Cc: Kris Kennaway <kris@obsecurity.org> Subject: Re: WITNESS bug Message-ID: <41758F2E.3060706@elischer.org> In-Reply-To: <200410191729.42330.jhb@FreeBSD.org> References: <20041019023713.GA1072@green.homeunix.org> <200410191650.28544.jhb@FreeBSD.org> <4175862C.6030403@elischer.org> <200410191729.42330.jhb@FreeBSD.org>
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John Baldwin wrote: >On Tuesday 19 October 2004 05:25 pm, Julian Elischer wrote: > > >>John Baldwin wrote: >> >> >>>On Tuesday 19 October 2004 12:01 pm, Kris Kennaway wrote: >>> >>> >>>>On Tue, Oct 19, 2004 at 09:13:26AM -0400, Robert Huff wrote: >>>> >>>> >>>>>Brian Fundakowski Feldman writes: >>>>> >>>>> >>>>>>You should never not run with WITNESS_SKIPSPIN if you use >>>>>>modules. Any spin mutexes not listed statically in the witness >>>>>>code will cause your machine to immediately panic. >>>>>> >>>>>> >>>>> If this is true (and I'm not disputing it), shouldn't it be >>>>>noted in GENERIC and/or NOTES? For that matter, what's the penalty >>>>>for not automatically including it as part of WITNESS? >>>>> >>>>> >>>>Sometimes you don't want to use it, e.g. if you actually want to trace >>>>spinlock operations with witness. >>>> >>>> >>>True spin mutexes should be rarely used anyways, so I don't think modules >>>needing spin mutexes is all that big of an issue. Almost all mutexes >>>should just be regular mutexes. >>> >>> >>netgraph uses a spin mutex for it's node locks >> >> > >This is likely a bug, esp. given that normal mutexes adaptively spin when it >is advantageous to do so. :) > > it assumes it's not going to sleep.. > > >
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