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Date:      Thu, 10 May 2001 12:40:42 -0400 (EDT)
From:      Robert Watson <rwatson@FreeBSD.ORG>
To:        Garrett Wollman <wollman@khavrinen.lcs.mit.edu>
Cc:        freebsd-current@FreeBSD.ORG
Subject:   Re: pgm to kill 4.3 via vm
Message-ID:  <Pine.NEB.3.96L.1010510123858.4086A-100000@fledge.watson.org>
In-Reply-To: <200105092117.RAA74500@khavrinen.lcs.mit.edu>

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On Wed, 9 May 2001, Garrett Wollman wrote:

> <<On Tue, 8 May 2001 23:31:51 -0400 (EDT), Robert Watson <rwatson@FreeBSD.ORG> said:
> 
> > I followed everything here fine until you asserted that the debugger
> > shouldn't need any locks.
> 
> When the debugger is running, everything else should have been
> forcibly halted.

The process and signal-related structures may be inconsistent if the
debugger disregards existing locks held over those structures.  It does
not matter if code is currently still executing, it matters that
preemption can occur.  The choices appear to be:

1) Disregard locks and risk corruption

2) Fail if a lock is held

Note that in either case (1) or case (2), the debugger may need special
code paths to implement services such as psignal() to indicate that
locking is either not needed, or that it should fail rather than
block/spin/...

Robert N M Watson             FreeBSD Core Team, TrustedBSD Project
robert@fledge.watson.org      NAI Labs, Safeport Network Services



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