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    SubjectRe: [RFC][PATCH 7/7] lockdep: spin_lock_nest_lock()
    On Mon, Aug 04, 2008 at 06:38:55PM +0200, Peter Zijlstra wrote:
    > You also need CONFIG_PROVE_LOCKING, but I'll assume that's set too.

    Sorry, that wasn't the problem, but my current testing passed because
    of another error... to test this report I rebuilt a kvm configured for
    rhel not for mainline so it wasn't the right test...

    When "long ago" I tested that this was working fine (actually when
    Andrew asked me), I guess lockdep was working because the
    implementation with the vmalloc array was slightly different,
    otherwise I don't know. I'm fairly certain that it worked fine at some
    point, and I didn't expect the refactoring to generate false positives.

    > Dave Jones just handed me:
    >
    > https://bugzilla.redhat.com/show_bug.cgi?id=457779

    I can reproduce this now yes after a 'make sync'.

    Obviously this is a bug in lockdep that it trips over this otherwise
    if lockdep was right the kernel should deadlock while this is just a
    false positive and everything runs fine.

    I assume it can't understand the spinlock address is different (I
    think it uses the address as key only for static locks), so I wonder
    if you could call print_deadlock_bug() from the failure path of the
    spinlock to solve this?

    Do things like double_rq_lock works just because rq1 and rq2 don't
    have the same name like in my case where all locks are called "mapping"->?

    > David Miller just did a patch that might fix that.

    Woow cool, after 11 months I lost any hope that lockdep could ever
    work in that environment... Was it an actual bug or is this some way
    to lower the complexity of the graph build?


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