Re: [PATCH] ppc64: Fix possible race with set_pte on a present PTE

David Mosberger
2004-05-27T21:56:33Z

>>>>> 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