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DragonFly bugs List (threaded) for 2009-12
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Re: panic: assertion: pmap->pm_stats.resident_count > 0 in pmap_release_free_page

From: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx>
Date: Tue, 29 Dec 2009 22:36:35 -0800 (PST)

    I think I found it.  It's a bug in zalloc, in vm/vm_zone.c.

	    fetch http://apollo.backplane.com/DFlyMisc/pmap04.patch

    Remove all the other patches and just throw in that one.  The pmap
    code uses zbootinit() and zinitna().  zbootinit() takes a fixed
    item array and uses the structure size as-is.  zinitna() rounds-up
    the structure size to a 32 byte boundary.  The pv_entry structure
    is 28 bytes.

    That blows up the calculation when the zone is expanded and creates
    an overlap, thus corrupting one of the pv_entry's.

    I found it when I added another field to pv_entry and suddenly the
    panic stopped occuring on my test box.

    There are still a few bugs in pmap.c which I will commit from the
    other patches.  As soon as I verify that the bug is in zalloc
    I will clean up the pmap.c patch and commit it along with the zalloc

    OMG this one was hard to find.  Of course, I haven't verified that
    it's the cause yet but it just has to be it.  So if it isn't I will


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