Date: Wed, 13 Dec 2006 20:10:49 +0800 From: David Xu <davidxu@freebsd.org> To: freebsd-java@freebsd.org, Daniel Eischen <deischen@freebsd.org> Cc: Kostik Belousov <kostikbel@gmail.com>, Poul-Henning Kamp <phk@phk.freebsd.dk>, "Arne H. Juul" <arnej@pvv.ntnu.no>, Bruce Evans <bde@zeta.org.au>, freebsd-arch@freebsd.org Subject: Re: close() of active socket does not work on FreeBSD 6 Message-ID: <200612132010.49601.davidxu@freebsd.org> In-Reply-To: <Pine.GSO.4.64.0612121543220.8780@sea.ntplx.net> References: <32874.1165905843@critter.freebsd.dk> <Pine.GSO.4.64.0612121543220.8780@sea.ntplx.net>
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On Wednesday 13 December 2006 04:49, Daniel Eischen wrote: > On Tue, 12 Dec 2006, Poul-Henning Kamp wrote: > > In message <20061212160016.W56465@delplex.bde.org>, Bruce Evans writes: > >> On Mon, 11 Dec 2006, Daniel Eischen wrote: > >> > >> It's probably a nightmare in the kernel too. close() starts looking > >> like revoke(), and revoke() has large problems and bugs in this area. > > > > There is the distinctive difference that revoke() operates on a name > > and close() on a filedescriptor, but otherwise I agree. > > Well, if threads waiting on IO are interruptable by signals, > can't we make a new signal that's only used by the kernel > and send it to all threads waiting on IO for that descriptor? > When it gets out to actually setup the signal handler, it > just resumes like it is returning from an SA_RESTART signal > handler (which according to another posting would reissue > the IO command and get EBADF). Even if you have implemented the close() with the interruption, another thread openning a file still can reuse the file handle immediately, according to specifications, the lowest free file handle will be returned, if SA_RESTART is used, the interrupted thread restart the syscall, it will be using a wrong file, I think even if we have implemented the feature in kernel, useland threads still has serious race to fix. David Xu
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