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Date: Sat, 21 Aug 2004 23:49:36 -0500
From: Alan Cox <alc@cs.rice.edu>
To: Robert Watson <rwatson@FreeBSD.org>
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Subject: Re: cvs commit: src/sys/vm vm_fault.c
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On Sun, Aug 22, 2004 at 12:18:49AM -0400, Robert Watson wrote:
> 
> On Sun, 22 Aug 2004, Brian Fundakowski Feldman wrote:
> 
> > Also, it was the system_map lock, so it was a mutex, not an sx. 
> > 
> > /Goes back to trying to figure out wtf portupgrade -rR kde\* keeps
> > causing
> >  hangs, but only in X, not at the command line, and not seemingly
> >  dependant on AGP/X driver. 
> 
> I believe mutexes are alright also as long as you're careful about
> sleeping and lock order.  I.e., don't sleep while holding a
> non-funnel-like mutex, etc.
> 

We should never page fault on a system map.  If that happens to you,
it indicates an error.  (In-kernel maps on which we do page fault,
such as the pipe submap, are treated the same as user maps and utilize
an sx lock.)

Alan