From: Arnd Bergmann <arnd@arndb.de>
To: michal.simek@petalogix.com
Cc: Linux Kernel list <linux-kernel@vger.kernel.org>,
LTP <ltp-list@lists.sourceforge.net>,
John Williams <john.williams@petalogix.com>,
Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Grant Likely <grant.likely@secretlab.ca>,
subrata@linux.vnet.ibm.com
Subject: Re: mmap syscall problem
Date: Mon, 6 Jul 2009 10:05:35 +0200 [thread overview]
Message-ID: <200907061005.36094.arnd@arndb.de> (raw)
In-Reply-To: <4A519A70.50801@petalogix.com>
On Monday 06 July 2009, Michal Simek wrote:
> > Does this happen on microblaze-mmu or microblaze-nommu, or both?
> > The mmap code for the two is very different.
> >
> For MMU code.
Could this be a cache-aliasing problem? If your cache is 'virtually-indexed'
(most architectures are 'physically-indexed'), the kernel may have written
into different parts of the D-cache than what the user space is reading
from. If you have a write-through cache, that can explain why you only
see the stale data at the beginning of the page -- the cache controller
is still busy writing back the data when you start reading it from
DRAM through the cache alias.
If this is your problem, then you need to implement flush_dcache_page()
and other functions that maintain cache consistency. See
Documentation/cachetlb.txt and http://www.linuxjournal.com/article/7105
Arnd <><
next prev parent reply other threads:[~2009-07-06 8:05 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-03 12:37 mmap syscall problem Michal Simek
2009-07-03 15:02 ` Arnd Bergmann
2009-07-06 6:32 ` Michal Simek
2009-07-06 8:05 ` Arnd Bergmann [this message]
2009-07-06 12:07 ` Michal Simek
2009-07-06 12:14 ` Paul Mundt
2009-07-06 12:54 ` Michal Simek
2009-07-06 14:16 ` Arnd Bergmann
2009-07-06 14:43 ` Michal Simek
2009-07-06 15:05 ` Arnd Bergmann
2009-07-06 15:19 ` Michal Simek
2009-07-07 0:44 ` Valdis.Kletnieks
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