Date: Fri, 8 Aug 2008 17:16:12 -0700 From: Alfred Perlstein <alfred@freebsd.org> To: Peter Jeremy <peterjeremy@optushome.com.au> Cc: cvs-src@freebsd.org, src-committers@freebsd.org, Ed Schouten <ed@freebsd.org>, cvs-all@freebsd.org, John Baldwin <jhb@freebsd.org> Subject: Re: cvs commit: src/sys/dev/io iodev.c Message-ID: <20080809001612.GN16977@elvis.mu.org> In-Reply-To: <20080809001256.GL64458@server.vk2pj.dyndns.org> References: <200808081343.m78DhwYE068477@repoman.freebsd.org> <200808081226.32089.jhb@freebsd.org> <20080809001256.GL64458@server.vk2pj.dyndns.org>
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* Peter Jeremy <peterjeremy@optushome.com.au> [080808 17:13] wrote: > On 2008-Aug-08 12:26:31 -0400, John Baldwin <jhb@freebsd.org> wrote: > >It should be setting D_TRACKCLOSE though so that close() reliably clears the > >flag even in single-threaded processes. You can still get odd behavior if > >you explicitly open it twice in an app and then close one of the two fd's. > >You will no longer have IO permission even though you still have one fd open. > >However, if you do that I think you deserve what you asked for. :) > > That behaviour may be legitimate: Your code links with libraries foo and > bar that each independently open /dev/io so they can frob different things > in IO space. libfoo needs ongoing access to device foo and so keeps its > descriptor open. libbar only needs once-off access to device bar and so > closes /dev/io once it's finished its initialisation. Libraries foo and > bar are completely independent and shouldn't need to know anything about > each other and your app shouldn't need to know that libraries it's using > frob around in IO space. Sort of the same problem with sysv style fcntl locks. :( -- - Alfred Perlstein
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