cvs commit: src/sys/amd64/amd64 pmap.c src/sys/i386/i386 pmap.c

[Martin Blapp]

Hi Alan,

This commit makes my box crash with HEAD at startup. Please back it out
and investige why it happens. I'm pretty sure that it happens for RELENG_6 too.

Martin

Martin Blapp, <mb at imp.ch> <mbr at FreeBSD.org>
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On Wed, 27 Sep 2006, Alan Cox wrote:

> alc         2006-09-27 18:10:16 UTC
>
>  FreeBSD src repository
>
>  Modified files:        (Branch: RELENG_6)
>    sys/amd64/amd64      pmap.c
>    sys/i386/i386        pmap.c
>  Log:
>  MFC
>    Correct a very old and very obscure bug: vmspace_fork() calls
>    pmap_copy() if the mapping is VM_INHERIT_SHARE.  Suppose the mapping
>    is also wired.  vmspace_fork() clears the wiring attributes in the vm
>    map entry but pmap_copy() copies the PG_W attribute in the PTE.  I
>    don't think this is catastrophic.  It blocks pmap_remove_pages() from
>    destroying the mapping and corrupts the pmap's wiring count.
>
>    This revision fixes the problem by changing pmap_copy() to clear the
>    PG_W attribute.
>
>  Approved by: re (mux)
>
>  Revision   Changes    Path
>  1.516.2.8  +4 -3      src/sys/amd64/amd64/pmap.c
>  1.523.2.8  +5 -3      src/sys/i386/i386/pmap.c
>