From owner-freebsd-net@FreeBSD.ORG  Thu Aug 18 14:31:24 2005
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Date: Thu, 18 Aug 2005 07:31:24 -0700
From: Luigi Rizzo <rizzo@icir.org>
To: Stephan Uphoff <ups@tree.com>
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	from ups@tree.com on Thu, Aug 18, 2005 at 10:18:33AM -0400
Cc: arch@freebsd.org, Max Laier <max@love2party.net>, net@freebsd.org
Subject: Re: duplicate  read/write locks in net/pfil.c and netinet/ip_fw2.c
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On Thu, Aug 18, 2005 at 10:18:33AM -0400, Stephan Uphoff wrote:
> On Thu, 2005-08-18 at 03:57, Luigi Rizzo wrote:
...
> > In fact i don't understand why you consider spinning and sleeping
> > on a mutex two different things.
> 
> The major difference between sleeping (cv_wait,msleep,..) and blocking
> on a mutex is priority inheritance.
> If you need to be able to use (non-spin) mutexes while holding a
> [R|W]LOCK and use a [R|W]LOCK while holding a (non-spin) mutex then you
> need to implement priority inheritance for [R|W]LOCKs.

is that required (in FreeBSD, i mean) for algorithmic
correctness or just for performance ?

	cheers
	luigi