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    SubjectRe: linux-next oops in __lock_acquire for process_one_work
    On Wed, 9 May 2012, Peter Zijlstra wrote:
    > On Tue, 2012-05-08 at 11:11 -0700, Hugh Dickins wrote:
    > > Please send me the version of patch you'd like to put in
    > > (lest I make it up myself and you don't like the result).
    >
    > something like so?

    More like the one below: I'm not alone in preferring a comma between args!

    And you're not a believer in checkpatch.pl, I see: I've removed trailing
    spaces; but left the 85-col line, that's not a fight I'll have with you.

    I'll set it going when I get home later - thanks.

    Hugh

    ---
    include/linux/lockdep.h | 17 +++++++++++++++++
    kernel/timer.c | 4 +++-
    kernel/workqueue.c | 4 +++-
    3 files changed, 23 insertions(+), 2 deletions(-)

    diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
    index d36619e..968c3e2 100644
    --- a/include/linux/lockdep.h
    +++ b/include/linux/lockdep.h
    @@ -157,6 +157,23 @@ struct lockdep_map {
    #endif
    };

    +static inline void lockdep_copy_map(struct lockdep_map *to, struct lockdep_map *from)
    +{
    + int i;
    +
    + *to = *from;
    + /*
    + * Since the class cache can be modified concurrently we could observe
    + * half pointers (64bit arch using 32bit copy insns). Therefore clear
    + * the caches and take the performance hit.
    + *
    + * XXX it doesn't work well with lockdep_set_class_and_subclass(), since
    + * that relies on cache abuse.
    + */
    + for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
    + to->class_cache[i] = NULL;
    +}
    +
    /*
    * Every lock has a list of other locks that were taken after it.
    * We only grow the list, never remove from it:
    diff --git a/kernel/timer.c b/kernel/timer.c
    index a297ffc..6aa7ad8 100644
    --- a/kernel/timer.c
    +++ b/kernel/timer.c
    @@ -1102,7 +1102,9 @@ static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long),
    * warnings as well as problems when looking into
    * timer->lockdep_map, make a copy and use that here.
    */
    - struct lockdep_map lockdep_map = timer->lockdep_map;
    + struct lockdep_map lockdep_map;
    +
    + lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
    #endif
    /*
    * Couple the lock chain with the lock chain at
    diff --git a/kernel/workqueue.c b/kernel/workqueue.c
    index 5abf42f..7d77d1f 100644
    --- a/kernel/workqueue.c
    +++ b/kernel/workqueue.c
    @@ -1810,7 +1810,9 @@ __acquires(&gcwq->lock)
    * lock freed" warnings as well as problems when looking into
    * work->lockdep_map, make a copy and use that here.
    */
    - struct lockdep_map lockdep_map = work->lockdep_map;
    + struct lockdep_map lockdep_map;
    +
    + lockdep_copy_map(&lockdep_map, &work->lockdep_map);
    #endif
    /*
    * A single work shouldn't be executed concurrently by

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      Last update: 2012-05-09 01:21    [W:0.025 / U:87.272 seconds]
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