From owner-freebsd-hackers@FreeBSD.ORG  Thu Sep 10 06:55:57 2009
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Date: Wed, 9 Sep 2009 23:26:53 -0700
Message-ID: <1fa17f810909092326l1271df94t1dea5ac9d5deba1b@mail.gmail.com>
From: MingyanGuo <guomingyan@gmail.com>
To: freebsd-hackers@freebsd.org
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Cc: LI Xin <delphij@delphij.net>
Subject: How to prevent other CPU from accessing a set of pages before
	calling pmap_remove_all function
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Hi all,

I find that function pmap_remove_all for arch amd64 works with a time window
between reading & clearing the PTE flags(access flag and dirty flag) and
invalidating its TLB entry on other CPU. After some discussion with Li
Xin(cced), I think all the processes that are using the PTE being removed
should be blocked before calling pmap_remove_all, or other CPU may dirty the
page but does not set the dirty flag before the TLB entry is flushed. But I
can not find how to block them to call the function. I read the function
vm_pageout_scan in file vm/vm_pageout.c but can not find the exact method it
used.  Or I just misunderstood the semantics of function pmap_remove_all ?

Thanks in advance.

Regards,
MingyanGuo