Messages in this thread | | | Date | Thu, 01 Apr 2010 13:20:05 +0800 | From | Cong Wang <> | Subject | Re: [Patch] workqueue: move lockdep annotations up to destroy_workqueue() |
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Tejun Heo wrote: > Hello, > > On 04/01/2010 01:28 PM, Cong Wang wrote: >>> Hmmm... can you please try to see whether this circular locking >>> warning involving wq->lockdep_map is reproducible w/ the bonding >>> locking fixed? I still can't see where wq -> cpu_add_remove_lock >>> dependency is created. >>> >> I thought this is obvious. >> >> Here it is: >> >> void destroy_workqueue(struct workqueue_struct *wq) >> { >> const struct cpumask *cpu_map = wq_cpu_map(wq); >> int cpu; >> >> cpu_maps_update_begin(); <----------------- Hold >> cpu_add_remove_lock here >> spin_lock(&workqueue_lock); >> list_del(&wq->list); >> spin_unlock(&workqueue_lock); >> >> for_each_cpu(cpu, cpu_map) >> cleanup_workqueue_thread(per_cpu_ptr(wq->cpu_wq, cpu)); >> <------ See below >> cpu_maps_update_done(); <----------------- Release >> cpu_add_remove_lock here >> >> ... >> static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq) >> { >> /* >> * Our caller is either destroy_workqueue() or CPU_POST_DEAD, >> * cpu_add_remove_lock protects cwq->thread. >> */ >> if (cwq->thread == NULL) >> return; >> >> lock_map_acquire(&cwq->wq->lockdep_map); <-------------- Lockdep >> complains here. >> lock_map_release(&cwq->wq->lockdep_map); >> ... > > Yeap, the above is cpu_add_remove_lock -> wq->lockdep_map dependency. > I can see that but I'm failing to see where the dependency the other > direction is created. >
Hmm, it looks like I misunderstand lock_map_acquire()? From the changelog, I thought it was added to complain its caller is holding a lock when invoking it, thus cpu_add_remove_lock is not an exception.
Thanks!
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