Date: Mon, 10 Mar 2008 15:18:50 +0100 From: Skalla Raabjorn <skalla.raabjorn@gmx.de> To: freebsd-arch@freebsd.org Subject: Re: If GIANT is locked can the MPSAFE parts run in parallel? Message-ID: <20080310151850.6d8451ff@sol.hackerzberg.local> In-Reply-To: <20080310143919.V50827@fledge.watson.org> References: <20080310140753.24630bda@sol.hackerzberg.local> <20080310143919.V50827@fledge.watson.org>
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On Mon, 10 Mar 2008 14:45:36 +0100 (BST) Robert Watson <rwatson@FreeBSD.org> wrote: > > On Mon, 10 Mar 2008, Skalla Raabjorn wrote: > > > if GIANT is locked can the MPSAFE parts run in parallel? Like networking for > > example, as they have their own locks. > > Dear Skalla, > > Yes. Giant is [almost] a mutex like any other mutex, so as long as the MPSAFE > subsystem isn't being invoked by something holding Giant, it generally won't > run with it. Even if the network stack is sometimes executed with Giant held > (for example, when receiving a packet from SLIP), that doesn't prevent the > network stack from executing in parallel on other CPUs, it just serializes > with respect to other Giant holders executing. Thanks, that's all I wanted to know :)
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