From: Jeff Hartmann <jhartmann@valinux.com>
To: Timur Tabi <ttabi@interactivesi.com>
Cc: Roman Zippel <roman@augan.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: ioremap_nocache problem?
Date: Thu, 25 Jan 2001 10:04:47 -0700 [thread overview]
Message-ID: <3A705CAF.70909@valinux.com> (raw)
In-Reply-To: <20010125165001Z132264-460+11@vger.kernel.org>
Timur Tabi wrote:
> ** Reply to message from Roman Zippel <roman@augan.com> on Thu, 25 Jan 2001
> 17:44:51 +0100
>
>
>
>> set_bit(PG_reserved, &page->flags);
>> ioremap();
>> ...
>> iounmap();
>> clear_bit(PG_reserved, &page->flags);
>
>
> The problem with this is that between the ioremap and iounmap, the page is
> reserved. What happens if that page belongs to some disk buffer or user
> process, and some other process tries to free it. Won't that cause a problem?
The page can't belong to some other process/kernel component. You own
the page if you allocated it. The kernel will only muck with memory you
allocated if its GFP_HIGHMEM, or under certain circumstances if you map
it into a user process (There are several rules here and I won't go into
them, look at the DRM mmap setup for a start if your interested.) This
is the correct ordering of the calls (I was the one who added support to
the kernel to ioremap real ram, trust me.)
-Jeff
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next prev parent reply other threads:[~2001-01-25 17:04 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-01-23 10:30 Mark Mokryn
2001-01-23 16:53 ` Timur Tabi
2001-01-25 15:16 ` Stephen C. Tweedie
2001-01-25 15:56 ` Timur Tabi
2001-01-25 16:44 ` Roman Zippel
2001-01-25 16:49 ` Timur Tabi
2001-01-26 10:39 ` Stephen C. Tweedie
[not found] ` <20010125165001Z132264-460+11@vger.kernel.org>
2001-01-25 17:04 ` Jeff Hartmann [this message]
2001-01-25 17:11 ` Timur Tabi
[not found] ` <E14LpvQ-0008Pw-00@mail.valinux.com>
2001-01-25 17:47 ` Jeff Hartmann
2001-01-25 17:53 ` Timur Tabi
2001-01-26 10:43 ` Stephen C. Tweedie
2001-01-26 16:32 ` Eric W. Biederman
2001-01-26 19:22 ` Timur Tabi
[not found] ` <20010125175308Z130507-460+45@vger.kernel.org>
2001-01-25 18:13 ` Jeff Hartmann
2001-01-25 18:18 ` Timur Tabi
[not found] ` <E14Lqyt-0003z6-00@mail.valinux.com>
2001-01-25 18:46 ` Jeff Hartmann
[not found] ` <200101251556.f0PFuPd01743@mail.redhat.com>
2001-01-26 10:37 ` Stephen C. Tweedie
2001-01-23 18:12 ` Roman Zippel
2001-01-23 18:38 ` Timur Tabi
2001-01-24 0:50 ` David Wragg, David Wragg
2001-01-24 15:14 ` Timur Tabi
[not found] ` <E14LRce-0008FU-00@diver.doc.ic.ac.uk>
2001-01-24 15:39 ` David Wragg
[not found] ` <20010123183847Z131216-18594+636@vger.kernel.org>
2001-01-24 1:01 ` David Wragg
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