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From: Bill Fenner <fenner@research.att.com>
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To: bde@zeta.org.au
Subject: Re: cvs commit: src/sys/fs/fifofs fifo_vnops.c
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>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.

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

  Bill

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