[issue1672] panic (trap 12) around btree_search() in 2.4.1-RELEASE

[Matthew Dillon]

:New submission from Joe "Floid" Kanowitz <jkanowitz at snet.net>:
:
:Using 2.4.1 with the lone patch from http://bugs.dragonflybsd.org/issue1583
:
:DragonFly tucker 2.4.1-RELEASE DragonFly v2.4.1.40.ga038d-RELEASE #1: Sat Jan 30
:11:57:51 EST 2010     root at tucker:/usr/obj/usr/src/sys/GENERIC  i386
:
:... I'm not sure when this occurred; possibly during nightly cleanup.
:The previous evening gave HAMMER a little more stress than usual via a bit of
:`undo` usage (normally none) which did seem to be turning up transient(?)
:"ITERATE ENTIRE HISTORY: Unknown error: 0" results similar to
:http://leaf.dragonflybsd.org/mailarchive/users/2009-09/msg00062.html (but here
:the HAMMER config is left at the sane defaults).  Not intending to poke at them
:too much unless it relates to the panic here.
:
:Couldn't get a dump because I didn't realize I hadn't specified a dumpdev (doh!).
:
:db> trace                                                                       
    I think the 'iterate entire history: unknown error: 0' was cockpit
    trouble in the hammer ioctl code and not a real error.  It was
    fixed in 2.5.x.

    The panic you got looks like it was an assertion instead of a
    seg-fault, because the backtrace was btree->panic instead of
    btree->trap->panic.

    Methinks the panic message must have scrolled off the screen
    (it would have been above the backtrace).  The trap below the
    trace was probably a double-fault in the debugger.

    Definitely set up your dumpdev so we can get a dump if this 
    occurs for you again.  There have been a couple of assertions
    fixed in 2.5.x that have not been MFCd to 2.4.x due to the
    HAMMER codebase diverging too much between 2.4.x and 2.5.x.

					-Matt