WG15 Defect Report Ref: 9945-1-amd1-04
Topic: mmap

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


Last update: 1997-05-20



 	 Defect Report Number:   9945-1-amd1-4
        Topic:                  mmap
        Relevant Sections:      12.2.1
        Classification:         (to be assigned)

Defect Report:

Date: Fri, 28 Oct 1994 09:16:14 -0500
From: willcox@urbana.mcd.mot.com (David A. Willcox)

I would like to request a formal interpretation on ISO/IEC
9945-1-amd1-1993, Real Time Extensions.

ISO/IEC 9945-1:1990 defines file times (access time and modification
time), and specifies in detail how functions in that standard effect the
file times.

ISO/IEC 9945-1-amd1-1993 adds the mmap() function (12.2.1) as a completely
new way to access a regular file.  However, It does not seem to specify
how accesses to a file via mmap() affect the file times.

To be specific, when shall, and when may, the implementation mark
st_atime and st_mtime for update in each of the following cases:

(1) mmap() is called with PROT_READ.
(2) mmap() is called with MAP_SHARED and PROT_WRITE.
(3) Application modifies a page previous mapped with MAP_SHARED, PROT_WRITE.
(4) Application references a page mapped MAP_PRIVATE that has
    not been modified by the process.  (Keep in mind that the process
    might be seeing data that has changed since the mmap().)
(5) Application modifies a page mapped MAP_PRIVATE, PROT_WRITE.
(6) Application references a page mapped MAP_PRIVATE that was
    previously modified by the process.
(7) msync() (12.2.4) is called on pages mapped with mmap().

WG15 response for 9945-1-amd1-1993
The standard is silent on this matter.  The committee notes that this is
inconsistent with page 27 line 626 which states generally that it should
specified and this matter is being referred to the sponsor for consideration.