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Date: Fri, 5 Jan 2007 11:34:36 -0500
From: Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: 1.7.0 CVS mmap failure
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On Fri, Jan 05, 2007 at 08:17:51AM -0800, Christopher Layne wrote:
>mmap() is supposed to zero-fill, not refuse to map when len
>is less than the system page size. I have never ever seen
>mmap() fail to map less than page size on any typical Posix
>system.
>
>"
>       The  system shall always zero-fill any partial page at the end
>       of an object. Further, the system shall never write out any
>       modified portions of the last page of  an  object  which are
>       beyond its end.    References within the address range starting
>       at pa and continuing for len bytes to whole pages following the
>       end of an object shall result in delivery of a SIGBUS signal.
>"
>
>Back to the original issue, consider this:
>
>MEM_TOP_DOWN
>0x100000	Allocates memory at the highest possible address.
>
>If there were any kind of simple arithmetic bug behind mmap()'s
>scenes (such as computing space to zero-fill, etc. etc.) I would
>think ENOMEM would be a very common scenario if we're allocating
>near the end of addressible space.

  % grep "simple arithmetic bug" mmap.cc
  %

Seems fine to me.

It's probably a hyperthreaded, dual-core problem.

cgf

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