From: Pavel Machek <pavel@ucw.cz>
To: Rik van Riel <riel@redhat.com>
Cc: rwhitton@iee.org, linux-kernel@vger.kernel.org
Subject: Re: Background memory scrubbing
Date: Sun, 24 Apr 2011 22:47:25 +0200 [thread overview]
Message-ID: <20110424204447.GA2467@ucw.cz> (raw)
In-Reply-To: <4DAF1DA7.9040705@redhat.com>
Hi!
> >>>for each PFN from 256 to the highest valid PFN
> >>>{
> >>>if (pfn_valid(PFN))
> >>>{
> >>>page = pfn_to_page(PFN)
> >>>va = kmap(page)
> >>>atomic_scrub(va, PAGE_SIZE)
> >>>kunmap(page)
> >>>}
> >>>
> >>>sleep(for_a_while)
> >>>}
> >>
> >>What exactly does atomic_scrub do?
> >
> >atomic_scrub is part of the edac subsystem see arch/x86/include/asm/edac.h. It simply does a locked add of zero to each DWORD in the specified range.
>
> I can think of only a few ways in which that could cause a
> kernel page fault.
>
> One of the more obvious causes would be running into an
> area of kernel memory that is mapped read-only. Writing
> to a page that is mapped read-only would cause a page
> fault :)
...also... you are actually making kernel use "self modifying code"
here. There are CPU bugs in that area... for example on K6.
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
next prev parent reply other threads:[~2011-04-25 11:41 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-20 17:05 Background memory scrubbing Robert Whitton
2011-04-20 17:53 ` Rik van Riel
2011-04-24 20:47 ` Pavel Machek [this message]
-- strict thread matches above, loose matches on Subject: below --
2011-04-20 15:46 Robert Whitton
2011-04-20 16:01 ` Borislav Petkov
2011-04-25 16:53 ` Chris Friesen
2011-04-20 14:40 Robert Whitton
2011-04-20 15:19 ` Clemens Ladisch
2011-04-20 15:35 ` Borislav Petkov
2011-04-20 15:46 ` Markus Trippelsdorf
2011-04-20 15:58 ` Borislav Petkov
2011-04-20 16:45 ` Markus Trippelsdorf
2011-04-20 16:55 ` Markus Trippelsdorf
2011-04-20 17:36 ` Borislav Petkov
2011-04-20 19:23 ` Bill Gatliff
2011-04-20 7:58 Robert Whitton
2011-04-20 13:30 ` Clemens Ladisch
2011-04-20 16:45 ` Rik van Riel
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