linux-kernel - Re: Concerning a post that you made about expandable anonymous shared mappings

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Message-ID: <4695CBC8.20508@gmail.com>
Date:	Thu, 12 Jul 2007 01:35:52 -0500
From:	William Tambe <tambewilliam@...il.com>
To:	Stas Sergeev <stsp@...et.ru>
CC:	Hugh Dickins <hugh@...itas.com>,
	"Rohland, Hans-Christoph" <hans-christoph.rohland@....com>,
	linux-kernel@...r.kernel.org
Subject: Re: Concerning a post that you made about expandable anonymous shared
 mappings



Stas Sergeev wrote:
> Hi.
> 
> William Tambe wrote:
>> I understand your concern. But since I am working on a dynamic memory 
>> management code that I wish to use with other projects that I have, I 
>> didn't find appropriate to use shm_open.
> Could you please provide a detailed list of the
> problems you have with shm_open? If they are
> valid, then I can bet the patch will be applied,
> no matter what. :)
> 
>> In fact there is a name associated with the shared memory requested 
>> with shm_open, so that it can be mmap(ed) in another process. And I do 
>> not wish to have it accessible by any other process, unless I choose 
>> to do so.
> In this case you need to use shm_unlink() right
> after shm_open(). Then this shm will be accessable
> only to your process and its children, via an fd,
> and not to anyone else. And you still can do anything
> with it (ftruncate/mmap/mremap whatever).
> 

Ok, now I find myself without any other arguments :-) shm_unlink() right 
after shm_open() is a solution.


>> And I think remap(ing) ANONYMOUS memory kind of make a lot of things 
>> easier.
> In what way, exactly?
> 
> 

I wrote the above not knowing that I could use shm_unlink() right after 
shm_open(). But still, I have lost a considerable amount of time trying 
to figure that out.
It appeared all natural to me that I could just remap ANONYMOUS and get 
what I wanted. And the worst thing here is that the man pages do not let 
you know about that.

Sincerely,
William Tambe
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