cvs commit: src/sys/amd64/amd64 pmap.c src/sys/i386/i386 pmap.c
scottl at samsco.org
Wed Sep 22 19:55:31 PDT 2004
Alan Cox wrote:
> alc 2004-09-22 05:01:48 UTC
> FreeBSD src repository
> Modified files:
> sys/amd64/amd64 pmap.c
> sys/i386/i386 pmap.c
> Correct a long-standing error in _pmap_unwire_pte_hold() affecting
> multiprocessors. Specifically, the error is conditioning the call to
> pmap_invalidate_page() on whether the pmap is active on the current CPU.
> This call must be unconditional. Regardless of whether the pmap is active
> on the CPU performing _pmap_unwire_pte_hold(), it could be active on another
> CPU. For example, a call to pmap_remove_all() by the page daemon could
> result in a call to _pmap_unwire_pte_hold() with the pmap inactive on the
> current CPU and active on another CPU. In such circumstances, failing to
> call pmap_invalidate_page() results in a stale TLB entry on the other CPU
> that still maps the now deallocated page table page. What happens next is
> typically a mysterious panic in pmap_enter() by the other CPU, either
> "pmap_enter: attempted pmap_enter on 4MB page" or "pmap_enter: pte vanished,
> va: 0x%lx". Both occur because the former page table page has been recycled
> and allocated to a new purpose. Consequently, it no longer contains zeroes.
> See also Peter's i386/i386/pmap.c revision 1.448 and the related e-mail
> thread last year.
> Many thanks to the engineers at Sandvine for providing clear and concise
> information until all of the pieces of the puzzle fell into place and
> for testing an earlier patch.
> MT5 Candidate
> Revision Changes Path
> 1.502 +6 -7 src/sys/amd64/amd64/pmap.c
> 1.508 +5 -10 src/sys/i386/i386/pmap.c
And thanks for your help too on this! Can I assume that this will be
merged to RELENG_5?
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