Date: Wed, 22 Sep 2004 20:54:03 -0600 From: Scott Long <scottl@samsco.org> To: Alan Cox <alc@FreeBSD.org> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/amd64/amd64 pmap.c src/sys/i386/i386 pmap.c Message-ID: <41523ACB.8090707@samsco.org> In-Reply-To: <200409220501.i8M51m8l009598@repoman.freebsd.org> References: <200409220501.i8M51m8l009598@repoman.freebsd.org>
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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 > Log: > 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? Scott
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