From owner-cvs-all  Sat Nov 10  2:48:58 2001
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Date: Sat, 10 Nov 2001 21:47:36 +1100 (EST)
From: Bruce Evans <bde@zeta.org.au>
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To: Bill Fenner <fenner@research.att.com>
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Subject: Re: cvs commit: src/sys/fs/fifofs fifo_vnops.c
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On Sat, 10 Nov 2001, Bill Fenner wrote:

> >For read(), it is normal to have to spin if there is no writer and you
> >don't want to block.
>
> You don't get a choice.  POSIX [seems to say] that a blocking read on
> a FIFO with no writers will return 0, forcing you to spin no matter what.

Oops.  (I think it is clear that POSIX actually says this.  So the only
way to avoid spinning is to do a blocking open().)

> FIFO permissions mean that it's possible that the reader cannot
> supply a phantom writer.

I forgot that you mentioned this before.

Bruce


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