Date: Thu, 02 Nov 2006 15:16:50 -0700 From: Scott Long <scottl@samsco.org> To: John Baldwin <jhb@freebsd.org> Cc: Perforce Change Reviews <perforce@freebsd.org>, Scott Long <scottl@freebsd.org>, Hans Petter Selasky <hselasky@c2i.net> Subject: Re: PERFORCE change 108878 for review Message-ID: <454A6E52.40207@samsco.org> In-Reply-To: <200611021231.53607.jhb@freebsd.org> References: <200611010112.kA11C1Jt066210@repoman.freebsd.org> <200611021151.19396.jhb@freebsd.org> <454A2679.4030609@samsco.org> <200611021231.53607.jhb@freebsd.org>
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John Baldwin wrote: > On Thursday 02 November 2006 12:10, Scott Long wrote: > >>John Baldwin wrote: >> >>>On Thursday 02 November 2006 06:22, Hans Petter Selasky wrote: >>> >>> >>>>On Wednesday 01 November 2006 16:47, John Baldwin wrote: >>>> >>>> >>>>>On Tuesday 31 October 2006 20:12, Scott Long wrote: >>>>> >>>>> >>>>>>http://perforce.freebsd.org/chv.cgi?CH=108878 >>>>>> >>>>>>Change 108878 by scottl@scottl-x64 on 2006/11/01 01:11:30 >>>>>> >>>>>>For some wonderful reason, you cannot pass &Giant to msleep. Work >>>>>>around that in a crude fashion. Also add some more assertions. >>>>> >>>>>Ah, yes, that would be most unhappy. I guess mostly the idea is that Giant >>>>>should be rather implicit and explicitly using Giant for an object lock is >>>>>discouraged. I'm not sure that is what you are doing though. I think >>>>>maybe you are borrowing Giant that's already held? >>>> >>>>I use this patch: >>>> >>>>/* preliminary fix for a bug in msleep on FreeBSD, >>>>* which cannot sleep with Giant: >>>>*/ >>>>#define msleep(i,m,p,w,t) msleep(i,(((m) == &Giant) ? NULL : (m)),p,w,t) >>>> >>>>Really this issue should be fixed. It happens just because GIANT_DROP is done >>>>too early in "msleep()". >>> >>> >>>Giant is special in msleep() and friends to make sure it is first in the >>>lock order, but unlock doesn't matter for lock order, and actually, the >>>current order is less intuitive. I think it's the way it is now because we >>>inherited it from BSD/OS. Also in theory old code under Giant should be >>>using tsleep() and not msleep() anyway. It actually won't hurt to move >>>DROP_GIANT later though. >>> >>>How about this: >>> >> >>This won't work for what I'm using it for. It's not a big deal, though. > > > ? It should make msleep(&Giant) work just the same as msleep(&foo). In this > case if Giant is only singly locked, DROP_GIANT just won't do anything. > Ah, ok, I didn't know that DROP_GIANT had that magic. Scott
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