lkml.org 
[lkml]   [2010]   [Apr]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [Patch] workqueue: move lockdep annotations up to destroy_workqueue()
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!


\
 
 \ /
  Last update: 2010-04-01 07:19    [W:0.095 / U:0.316 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site