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    SubjectRe: [PATCH] lockdep: lockdep_depth vs. debug_locks Re: [2.6.20] BUG: workqueue leaked lock
    On Wed, Mar 21, 2007 at 10:28:02PM -0800, Andrew Morton wrote:
    > On Thu, 22 Mar 2007 07:11:19 +0100 Jarek Poplawski <jarkao2@o2.pl> wrote:
    >
    > >
    > > Here is some joke:
    > >
    > > [PATCH] lockdep: lockdep_depth vs. debug_locks
    > >
    > > lockdep really shouldn't be used when debug_locks == 0!
    > >
    >
    > This isn't a very good changelog.
    >
    > >
    > > Reported-by: Folkert van Heusden <folkert@vanheusden.com>
    > > Inspired-by: Oleg Nesterov <oleg@tv-sign.ru>
    > > Signed-off-by: Jarek Poplawski <jarkao2@o2.pl>
    > >
    > > ---
    > >
    > > diff -Nurp 2.6.21-rc4-git4-/include/linux/lockdep.h 2.6.21-rc4-git4/include/linux/lockdep.h
    > > --- 2.6.21-rc4-git4-/include/linux/lockdep.h 2007-03-20 20:24:17.000000000 +0100
    > > +++ 2.6.21-rc4-git4/include/linux/lockdep.h 2007-03-21 22:32:41.000000000 +0100
    > > @@ -245,7 +245,7 @@ extern void lock_release(struct lockdep_
    > >
    > > # define INIT_LOCKDEP .lockdep_recursion = 0,
    > >
    > > -#define lockdep_depth(tsk) ((tsk)->lockdep_depth)
    > > +#define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0)
    > >
    > > #else /* !LOCKDEP */
    > >
    >
    > What problem does this solve, and how does it solve it?
    >
    > I assume that some codepath is incrementing ->lockdep_depth even when
    > debug_locks==0. Isn't that wrong of it?
    >

    This should definitely solve this problem - as it was said
    a few times before lockdep stops registering locks after
    a bug, so even the lock which caused the warning isn't
    reported. Here lockdep found a bug in a workqueue function,
    so after this no lock or unlock isn't counted nor reported.

    I think Ingo can tell more.

    Regards,
    Jarek P.
    -
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