Date: Fri, 28 May 2004 12:42:03 -0700 (PDT) From: Alan Cox <alc@FreeBSD.org> To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org Subject: cvs commit: src/sys/amd64/amd64 pmap.c src/sys/i386/i386 pmap.c Message-ID: <200405281942.i4SJg3aJ040317@repoman.freebsd.org>
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alc 2004/05/28 12:42:03 PDT
FreeBSD src repository
Modified files:
sys/amd64/amd64 pmap.c
sys/i386/i386 pmap.c
Log:
Remove a broken micro-optimization from pmap_enter(). The ill effect
of this micro-optimization occurs when we call pmap_enter() to wire an
already mapped page. Because of the micro-optimization, we fail to
mark the PTE as wired. Later, on teardown of the address space,
pmap_remove_pages() destroys the PTE before vm_fault_unwire() has
unwired the page. (pmap_remove_pages() is not supposed to destroy
wired PTEs. They are destroyed by a later call to pmap_remove().)
Thus, the page becomes lost.
Note: The page is not lost if the application called munlock(2), only
if it relies on teardown of the address space to unwire its pages.
For the historically inclined, this bug was introduced by a
megacommit, revision 1.182, roughly six years ago.
Leak observed by: green@ and dillon independently
Patch submitted by: dillon at backplane dot com
Reviewed by: tegge@
MFC after: 1 week
Revision Changes Path
1.461 +0 -8 src/sys/amd64/amd64/pmap.c
1.467 +0 -8 src/sys/i386/i386/pmap.c
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