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Date:      Mon, 18 Mar 2002 10:31:51 -0800
From:      Alfred Perlstein <bright@mu.org>
To:        John Baldwin <jhb@FreeBSD.org>
Cc:        Robert Watson <rwatson@FreeBSD.ORG>, smp@FreeBSD.ORG, current@FreeBSD.ORG, hitmaster2k@yahoo.com, phk@FreeBSD.ORG, tanimura@r.dl.itc.u-tokyo.ac.jp, Munehiro Matsuda <haro@h4.dion.ne.jp>
Subject:   Re: -current lock warning...
Message-ID:  <20020318183151.GA22622@elvis.mu.org>
In-Reply-To: <XFMail.20020318132404.jhb@FreeBSD.org>
References:  <Pine.NEB.3.96L.1020317120811.965J-100000@fledge.watson.org> <XFMail.20020318132404.jhb@FreeBSD.org>

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* John Baldwin <jhb@FreeBSD.org> [020318 10:24] wrote:
> 
> On 17-Mar-2002 Robert Watson wrote:
> > 
> > On Sun, 17 Mar 2002, Alfred Perlstein wrote:
> > 
> >> * Munehiro Matsuda <haro@h4.dion.ne.jp> [020317 06:36] wrote:
> >> > 
> >> > PS. I got another message that happend when I ^C'ed a buildworld earlier, 
> >> > with same kernel. May be it should go to Alfred Perlstein?
> >> > 
> >> > lock order reversal
> >> >  1st 0xc198eec0 pipe mutex @ ../../../kern/sys_pipe.c:779
> >> >  2nd 0xc0367fe0 Giant @ ../../../i386/i386/trap.c:716
> >> 
> >> I think there's a place where the pipe can fault on an address while
> >> copying, I'll take a look at this. 
> > 
> > Are there any assertions that should be in place for copyin/copyout
> > requring fault handling?  It sounds like somewhere we need to assert that
> > Giant is held...
> 
> More correct is that probably no locks other than Giant should be held for
> copyin/copyout.

s/probably/definetly.

Can you please provide a "blessed" API for raising and lowering a
"can't block" count in the thread?  This can be used in copyout,
copyin, and a bunch of vm and buffer ops to make sure we aren't calling
them with mutexes held.

-- 
-Alfred Perlstein [alfred@freebsd.org]
'Instead of asking why a piece of software is using "1970s technology,"
 start asking why software is ignoring 30 years of accumulated wisdom.'
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