Date: Tue, 27 Jan 2009 15:10:48 +0000 (GMT) From: Robert Watson <rwatson@FreeBSD.org> To: Julian Elischer <julian@elischer.org> Cc: arch@freebsd.org, Poul-Henning Kamp <phk@phk.freebsd.dk> Subject: Re: need for another mutex type/flag? Message-ID: <alpine.BSF.2.00.0901271509290.5592@fledge.watson.org> In-Reply-To: <497C249C.5060507@elischer.org> References: <23211.1232871523@critter.freebsd.dk> <497C249C.5060507@elischer.org>
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On Sun, 25 Jan 2009, Julian Elischer wrote: > Even purely documentary would be good but given the option, I'd like it to > scream when Witness is enabled and you try get another mutex.... > > there are certain contexts (e.g. in most netgraph nodes) where we really > want the authors to only take such locks and taking more unpredictable > mutexes plays havoc with netgraph response times as a system as a whole, > since if one node blocks, teh thread doesn't get to go off and service other > nodes. I thought lots of Netgraph nodes liked to do things like call m_pullup() and m_prepend()? Disallowing acquiring mutexes will prevent them from doing that. Robert N M Watson Computer Laboratory University of Cambridge
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