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    SubjectRe: [PATCH 0/2] lockdep vs recursive read locks
    On Wed, 12 Mar 2008, Peter Zijlstra wrote:
    > We seemed to have some lockdep trouble wrt recursive read locks. Today Gautham
    > asked me some specific questions about it, which led to these patches.
    >
    > IIRC Hugh ran into something similar a while back. This hopefully fixes it.

    Hmm, I don't remember that myself: can you jog my memory?

    What I do remember is that when I fixed madvise(MADV_REMOVE i.e. holepunch)
    not to hold mmap_sem (at that time down_write but today down_read, though
    would still be bad) across vmtruncate_range which takes i_mutex (contrast
    writing from an unfaulted area that takes i_mutex then down_read mmap_sem),
    Ingo asked me offline if lockdep caught that and it didn't. Just tried
    again now, with your patches applied, and madvise_remove restored to its
    old misbehaviour, and it looks like lockdep still doesn't catch it
    (but suspect me of pilot error if you find otherwise).

    Hugh


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