Date: Mon, 20 Feb 2006 13:43:48 -0500 From: John Baldwin <jhb@freebsd.org> To: Andrew Thompson <thompsa@freebsd.org> Cc: freebsd-current@freebsd.org Subject: Re: rwlock patch for bridge Message-ID: <200602201343.49927.jhb@freebsd.org> In-Reply-To: <20060219041012.GB78376@heff.fud.org.nz> References: <20060215211534.GA78376@heff.fud.org.nz> <200602171342.13451.jhb@freebsd.org> <20060219041012.GB78376@heff.fud.org.nz>
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On Saturday 18 February 2006 23:10, Andrew Thompson wrote: > On Fri, Feb 17, 2006 at 01:42:11PM -0500, John Baldwin wrote: > > On Wednesday 15 February 2006 16:15, Andrew Thompson wrote: > > > Here is a patch that changes if_bridge to use rwlock(9) rather than the > > > handrolled ref counting. Can I please get it reviewed to ensure I have > > > the changes correct. I pondered if the order of unlocking the softc > > > mutex and grabbing the rlock mattered but decided it didn't. > > > > Have you thought about replacing both the mutex and ref-count with the > > single rwlock? (Perhaps that is infeasible, but it would be somewhat > > pointless to just lock one lock so you can turn around and lock the > > next.) > > The bridge code makes use of callout_init_mtx(), can a rwlock be passed > instead of a mutex? No. You could use callout_init() and mark it MPSAFE and handle the teardown race yourself perhaps. I'd be interested in benchmarks, btw, of this patch as I'd imagine it is actually a pessimization because you are trading simple arith operations for atomic operations to mess with the rw lock. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org
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