Date: Mon, 17 Aug 2009 13:27:55 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: cvs-src-old@freebsd.org Subject: cvs commit: src/sys/amd64/amd64 pmap.c Message-ID: <200908171328.n7HDS5qC062689@repoman.freebsd.org>
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kib 2009-08-17 13:27:55 UTC
FreeBSD src repository
Modified files:
sys/amd64/amd64 pmap.c
Log:
SVN rev 196318 on 2009-08-17 13:27:55Z by kib
Correct a critical accounting error in pmap_demote_pde(). Specifically,
when pmap_demote_pde() allocates a page table page to implement a
user-space demotion, it must increment the pmap's resident page count.
Not doing so, can lead to an underflow during address space termination
that causes pmap_remove() to exit prematurely, before it has destroyed
all of the mappings within the specified range. The ultimate effect or
symptom of this error is an assertion failure in vm_page_free_toq()
because the page being freed is still mapped.
This error is only possible when superpage promotion is enabled. Thus,
it only affects FreeBSD versions greater than 7.2.
Tested by: pho, alc
Reviewed by: alc
Approved by: re (rwatson)
MFC after: 1 week
Revision Changes Path
1.668 +2 -0 src/sys/amd64/amd64/pmap.c
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