WG15 Defect Report Ref: 9945-1-amd1-09

This is an approved interpretation of 9945-1-amd1-1993.


Last update: 1997-05-20

                                                                9945-1-amd1-93 #9


	Defect Report Number: (to be assigned by WG15)
        Topic:                  _POSIX_PRIORITIZED_IO part 1
        Relevant Sections:
        Classification:         (to be assigned)

Defect Report:

From: "Frank Prindle" <prindle@voicenet.com>
Date: Tue, 28 May 1996 08:52:51 +0000

FOR ISO/IEC 9945-1-amd1-1993:

1b. Subsection, Page 152-153, Lines 729-732:

	Regarding the option identified by {_POSIX_PRIORITIZED_IO}, the
	statement says "When prioritized asynchronous I/O requests to the same
	file are blocked waiting for a resource required for that I/O operation,
	the higher-priority I/O requests shall be granted the resource before
	lower-priority I/O requests are granted the resource."  The statement
	is ambiguous with regard to the word "resource".

	Are the resources (to be considered) ONLY the resources managed by the
	OS implementation?  Once an output request, for example, has
	been passed from the OS to a smart controller or device, is that
	output considered completed as far as async I/O concerned?  Is the
	smart controller then permitted to re-order actual writes to a physical
	device without the knowledge of the OS (which claims to support
	the Prioritized I/O option)?

	Assuming that the interpretation answers "yes" to the above questions
	(which are all logically equivalent questions), I suggest that the
	semantics of the Prioritized I/O option be clarified to indicate that
	the "resource" referenced by this sentence is a resource for which
	contention is managed by the OS implementation, and not resources
	invisible to the OS implementation.

WG15 response for 9945-1-amd1-1993

The standard is clear.  On page 152 lines 723-727 it states that for
character special files the requests are processd in FIFO order by the
underlying device and for any other type, the order of processing is


Forwarded to Interp group chair: 5/28/96
Finalised: 6/25/96