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From: David Mosberger <davidm@napali.hpl.hp.com>
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Date: Thu, 27 May 2004 14:56:33 -0700
To: Andrea Arcangeli <andrea@suse.de>
Cc: davidm@hpl.hp.com, Linus Torvalds <torvalds@osdl.org>,
       Benjamin Herrenschmidt <benh@kernel.crashing.org>,
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Subject: Re: [PATCH] ppc64: Fix possible race with set_pte on a present PTE
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>>>>> On Tue, 25 May 2004 06:53:22 +0200, Andrea Arcangeli <andrea@suse.de> said:

  >> If the "accessed" or "dirty" bits are zero, accessing/writing the
  >> page will cause a fault which will be handled in a low-level
  >> fault handler.  The Linux version of these handlers simply turn
  >> on the respective bit.  See daccess_bit(), iaccess_bit(), and dirty_bit()
  >> in arch/ia64/kernel/ivt.S.

  Andrea> so you mean, this is being set in the arch section before
  Andrea> ever reaching handle_mm_fault?

Correct.  The low-level fault handlers set the ACCESSED/DIRTY bits
with an atomic compare-and-exchange (on SMP).  They don't (normally)
bubble up all the way to the Linux page-fault handler.

	--david