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Date: Mon, 16 Apr 2001 10:26:16 -0700
From: Andrew Morton <andrewm@uow.edu.au>
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To: yodaiken@fsmlabs.com
CC: Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: rw_semaphores
In-Reply-To: <Pine.LNX.4.31.0104092242320.11520-100000@penguin.transmeta.com> <8623.986888854@warthog.cambridge.redhat.com>,
		<8623.986888854@warthog.cambridge.redhat.com>; from dhowells@cambridge.redhat.com on Tue, Apr 10, 2001 at 08:47:34AM +0100 <20010416083912.C4036@hq.fsmlabs.com>
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yodaiken@fsmlabs.com wrote:
> 
> On Tue, Apr 10, 2001 at 08:47:34AM +0100, David Howells wrote:
> >
> > Since you're willing to use CMPXCHG in your suggested implementation, would it
> > make it make life easier if you were willing to use XADD too?
> >
> > Plus, are you really willing to limit the number of readers or writers to be
> > 32767? If so, I think I can suggest a way that limits it to ~65535 apiece
> > instead...
> 
> I'm trying to imagine a case where 32,000 sharing a semaphore was anything but a
> major failure and I can't. To me: the result of an attempt by the 32,768th locker
> should be a kernel panic. Is there a reasonable scenario where this is wrong?
> 

It can't happen (famous last words).

- It is a bug for a task to acquire an rwsem more than once
  (either for read or write), so we don't do this.

- Linux only supports, err, 31700 user processes.
-
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