Re: mmap() of /dev/kmem issue

Grant Grundler
2004-05-04T17:19:58Z

On Tue, May 04, 2004 at 11:30:21AM -0500, Mario Smarduch wrote:
> I have problem of viewing memory contents via mmap() of /dev/kmem.

1) which regions/addresses are you accessing?
2) what values do you see/should see?
3) test case?

grant

> After mmap()'ing /dev/kmem for reading
> it appears that data accessed in the kernel lives in
> different cache lines from data accessed in the user space.
> The lseek()/read() from kernel reflects latest updates,
> but same reads from user space mmap fetches old data, and
> vice versa when updating from user. When I flush the
> caches (cat of a big file to another file), then user mapped
> value reflects the latest changes but then again remains
> frozen. I'm having trouble understanding how can this
> happen since the caches are physically indexed.
> Any ideas what the problem could be?
>
> - Mario.
>
> -
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