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    SubjectRe: [RFC/PATCH] debug workqueue deadlocks with lockdep

    * Johannes Berg <johannes@sipsolutions.net> wrote:

    > > > @@ -257,7 +260,9 @@ static void run_workqueue(struct cpu_wor
    > > >
    > > > BUG_ON(get_wq_data(work) != cwq);
    > > > work_clear_pending(work);
    > > > + lock_acquire(&cwq->wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
    > > > f(work);
    > > > + lock_release(&cwq->wq->lockdep_map, 0, _THIS_IP_);
    > > ^^^
    > > Isn't it better to call lock_release() with nested == 1 ?
    >
    > Not sure, Ingo?

    well, in this case the lock/unlock should nest perfectly (i.e. it should
    always be balanced perfectly), so indeed calling with nested==1 leads to
    stricter checking.

    non-nested unlocks occur when people do stuff like:

    spin_lock(&lock1);
    spin_lock(&lock2);
    spin_unlock(&lock1);
    spin_unlock(&lock2);

    the first unlock is not 'nested perfectly'. Now for the workqueue
    dep_map this shouldnt be a legal combination, right?

    Ingo
    -
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